| Turning Thin Washers or Spacers
(Aug 12, 2001) |
Finish problem (Apr 10,
2004) |
| Cast iron machining (Oct
4, 2001) |
Turning, Boring... Titanium
(Apr 12, 2004) |
|
Steel (Feb 3, 2002) |
Dialing in to center
(Apr 26, 2004) |
| Use of a center finder
(Jul 21, 2002) |
Turning radii (May 2,
2004) |
| Layout Question (Aug 14,
2002) |
Steel (May 4, 2004) |
| When I machine I get this
(Aug 30, 2002) |
How do I radius corners?
(May 6, 2004) |
| Disc facing (Sep 9, 2002) |
Heavy 10 vibration (May
26, 2004) |
| Black finishes (Sep 10,
2002) |
Large dia. turning on a 9"
(Jun 5, 2004) |
| Turning question (Sep 13,
2002) |
Spinning aluminum (Sep
19, 2004) |
| Vibe trail? (Oct 9, 2002) |
Turning a concave radius (Sep 22, 2004) |
| Vibration problem (Oct
11, 2002) |
Turning a CONVEX radius (Sep 23, 2004) |
| Rings on workpiece (Nov
2, 2002) |
Machined finish expectations (Sep 24, 2004) |
| How to cut shims? (Nov
17, 2002) |
Maximum depth of cut turning mild steel (Nov 1, 2004) |
| Turning plastics (Dec
10, 2002) |
Turning Titanium (Nov 13, 2004) |
| Vibration Question from a newbie
(Dec 28, 2002) |
Turning barstock (Nov 25, 2004) |
|
Fixturing question (Mar 10, 2003) |
On-center tool use (Jan 10, 2005) |
| Lathe Vibration? (Apr
13, 2003) |
Turning 4130 Chrome Moly (Jan 24, 2005) |
| Large objects on faceplate
(Jun 9, 2003) |
Turning 430 Stainless
(Jan 30, 2005) |
| Turning Troubles (Jun
23, 2003) |
How to set angles (Feb
1, 2005) |
| Turning Large Diameter Stock
(Jul 3, 2003) |
Attaching outboard spider
(Feb 24, 2005) |
| Surface Finish (Jul 4,
2003) |
Helical pattern in part
(Mar 8, 2005) |
| Finishing (Jan 26, 2004) |
|
| |
| Turning Thin Washers or Spacers |
| I'm
attempting to make some spacers roughly .06" thick from a short
piece of steel tubing with an inner diameter of 1" and a wall
thickness of roughly 1/8". I've had pretty mixed results, so far. I
can face on one side with no problem, but facing the back side and
cutting the spacer off the tubing is problematic. Anyone tried this
with any degree of success? Jim
(1294) |
| There is the jewelers way of doing
this which works pretty well. What you do what you are doing and
part off the piece at a thickness that work reliably then take
something like a piece of brass and turn yourself a fixture that the
piece will just slide on front first. Then use a bit of crazy glue
and glue the piece to the fixture then face off the back side to
thickness. Then throw the whole affair is some lacquer thinner of
release agent for the crazy glue and you have your part.
Yasmiin (1295) |
| Jim, Here are some
other methods: It would be much simpler if you had access to a
surface grinder, but I'll limit it to machining on a lathe. One way
would be to make an initial parting cut, not all the way through.
Then machine the backside of the washer. Then complete the cut off
process, deburr both OD edges before final cutoff. Another method
would be to cutoff a bit thicker say .010 or so. I'd bore the ID
with this method. Then I'd make an expanding arbor out of aluminum.
Basically, drill and tap for a pipe thread, then make cross cuts in
an X patters or 6 slots across. Then in the lathe machine the OD
.001 undersize of the ID of the washer and only .050 back. If the
bore of the washer is true then it should face reasonably flat.
Place washer on arbor and tighten in the pipe threads (get some type
of pipe fitting). Then face the part. I'd deburr the OD edges with a
file on the lathe (use a handle on the file for safety) Still another
method would be to find some washers with the thickness and ID you
desire. Make a mandrel with an OD .001 under the ID of the
washers. Make an end plate to be bolted on the end of the mandrel OD
a bit under the OD desires. You can turn 5 or more at one time. Just
make the length of the mandrel just a bit less than the thickness of
the washers. Then tighten and machine the OD down to the desired OD.
T G Brandl (1304) |
| I should clarify method 1. First face
and deburr the front 2 edges (ID, OD). Next, Set up to cutoff the
part. Start a cutoff at .010 longer than what your final
length (thickness) will be. Turn in till you have .020 left to cut
off. This should hold the part on. Move the cutoff tool back to
take off .005 more down to the same depth as before. Take off the
rest of the material off the back face down to the same diameter.
The part should still be left on. Next deburr the OD edge of the
back side with a file. Then forward the cutoff tool about .002, so
it wont take a cut. I'd keep the cutoff tool as short as possible
to minimize flexing. Cut all the way through. It should leave only a
thin ring on the inside edge. I find I can remove this ring with
wire nippers. Then deburr the ID edge with a deburr tool. T G
Brandl (1308) |
| Cast iron machining |
| Sand-cast iron as
made into parts that are intended to be machined in industry ( like
pipe fittings, etc.) is usually annealed in an oven after casting
and before machining - this makes it more uniform in texture and
generally softer, also more resistant to cracking from retained
stresses. Lots of other CI is not annealed because it costs too much
and the one selling it doesn't have to machine it, or the machining
operation is a smaller part of the item final cost so they just live
with the lesser tooling lifetime. Most all CI ( actually all
sand-cast metal) is very likely to have ( sand grains) inclusions in
the first say 10-30 thousandths skin depth which will make
microscopic chips in almost all cutters eventually. ( sandblast a
carbide tool surface and see what happens). The type and maintenance
of the sand, molding operation, casting metallurgy and core handling
and hygiene all contribute to the amount of included grit in the
cast. There is carbide tooling made for cutting cast iron that holds
up pretty well but they cost more and have their own problems -
chips, overheats, material sticks, etc. (really challenging to
re-sharpen properly.) A cobalt cutter properly ground gives good
surface finish, can take a fairly heavy cut and not deflect or
overheat, and is good and cheap, easily re-sharpened, M2 type - HSS
is same. Let's remember that in machining everything, tooling edge
is a consumable item: it is used up in the process of generating the
cut. The thing that changes is how long it lasts and what is the
cost of restoring it. There is no amount of care that will keep a
given metal cutting edge good forever ( even diamond wears) - unless
maybe you are cutting a lot of Jell-O? The best approach is to have a
good grinder and handstone technique, and practice sharpening
tooling often - then it is a small and easily accomplished item to
put in a fresh edge and set up the next cut. Most of us will never
be knowledgeable or lucky enough to select just the right casting
or exactly the right tool for cutting each individual one, but we
can probably all learn to make a good setup, a good cut, sharpen the
tool, and go on with the project. Lets not get wrapped around the
axle on the minutiae that we can't escape. The technique of making a
hole in the skin only works at the one point and doesn't affect the
tool wear as it traverses the cast surface - the tool edge doesn't
care if it hits the grit particle from top or side - it still gets
scratched if the grit is harder than the tool material. Making a
hole only helps in the hardness area if the cut is deeper than the
skin hardness layer and the tool has a sharper or more durable edge
on the side where it will contact the material than on the point
that is plunged to penetrate the layer. If you think about it -
didn't we all know this already? (1725) |
| Steel |
| Paul, unless you
have a raving desire to case-harden, stay away from cold-rolled. It
is a poor mans steel and to damn much stuff is made from it, (only my
opinion!). For your project I would go with 1144 or 4140 machine
steel. Takes a good finish and is a bit tougher. What you want are 2
things. A tough machineable steel that has good finishing
characteristics. If I were making a machine-tool I'd go directly to
tool steel made in USA. Carpenter Steel if I could get it! Not only
is tool steel heat-treatable, it is more homogenous (more organized
if you like). It has no pockets of hard and soft, (I don't like
surprises!!). OK so it's expensive, so is your time and frustration
level. Every once in a while, you need to go out and do something
that turns into gold instead of lead. You buy that chunk of steel
and turn it into gold! Ron
(3061) |
| The difference between
hot rolled (HRA) and cold rolled or cold drawn steel is not the
chemistry of the steel but the way its finished at the mill. You can
have the same grade (chemistry) of steel, but finished different
ways. Hot rolled is the way it comes off the mill. If it is to be
drawn, they leave it a little oversize, then run it through dies to
smooth out the finish, while bringing it to size. This puts stress
into the material. Once its drawn they straighten the mat'l. Now its
straight but still has the stress in it. Cold drawn has more stress
than cold rolled. This material has many drawbacks but also many
good uses. Usually cold drawn/rolled mat'l is very close to a
nominal size so you don't have to do to much to the thickness of it.
If you do it is best to do the same to both sides equally. this will
help reduce warpage, but don't count on it. Lets say you had to make
a 1/4" thick x 2" x 8" bracket with holes in it. If you get 1/4"
cold rolled/drawn x 2 mat'l, all that's needed is to put the holes
in it. If you use 1/4" hot rolled, it will measure appx .275/.285 on
the thickness, Which would be fine unless you need it to be
.248/.252.(its also oversize on the width) I make a lot of High
Speed Steel tools out of both Cold worked Hra mat'l. Both serves its
purpose. The easiest way to tell the difference is how sharp the
edges are on the bar. Cold drawn is sharp while hra is more rounded.
Mike
(3064) |
| Ron, I was doing a little reading and 1144 (stressproof)
sounds interesting. I had to dig around on the net a little as my
copy of Machinery's Handbook is from 1946 (hey, I like old books)
and didn't appear list it. Since there's no way I'll harden or case
harden this dividing head spindle, it sounds like a good compromise
between machinability and strength. At least it's not too expensive
so I can afford to experiment with it. Some day if I get an O/A
welding setup I'll try case hardening some big pieces like this.
Paul R. (3069) |
| I've done a bit with 1144
lately and I like it. It machines fairly well, and is far less
stringy than stuff like drill rod. I did ruin some HSS steel tooling
on it when the spindle speed got too high, but at reasonable speeds
with hss (or high speeds with carbide) it cuts nicely. I will
mention though that the smaller (1/2" dia) stock I got from McMaster
was not quite straight - no problem over short distances, but it
wobbled around a little more than drill rod does when I set up a
three foot piece between steady and follower rests. Chris (3074) |
| Use of a center
finder |
| On page 54 of How
To Run A Lathe they describe the use of a center finder. It is not
clear to me how this device is mounted and used. Chris (5254) |
| By placing the end
of a pointed rod in the "pop" mark and spinning the lathe slowly,
you can "see" if the "pop" mark is running true. Actually, you can
either watch the distance between the cutter and the rod vary, or
use a DI with an elephant's foot (like a nail head) on it mounted in
place of the cutter. Paul R. (5256) |
| Paul, but
I'm still not clear on what is holding this rod in the center POP.
Chris (5258) |
| The other end is
held in the tailstock. There is (I would guess) a 60 degree
depression in that end of the rod, and a 60 degree point on the
"business end" of the rod. Pressure applied via the tailstock with a
60 degree center keeps the rod in the "pop" mark on the work piece
in the spindle chuck. I made one that has a spring on the tailstock
end so that I can safely apply tailstock pressure and not worry
about too much or too little pressure to hold the rod. Another way
to align a workpiece for drilling or boring is a "Toolmaker's
Button" which is a precision-ground hollow cylinder typically 1/2
inch diameter and about 1/2" tall. You drill and tap a hole as close
as you can to the center you want. Bolt the toolmaker's button to
the spot, and since the hole through the button is larger than the
bolt, you can move the button around a little while the bolt is
loose to set the button exactly, and then tighten the bolt on the
button. Now mount the workpiece on the lathe and set the button to
run true using a DTI. Remove the button and do your precision
drilling/boring. I've got a nice old set of Starrett buttons that I
use. Paul R. (5260) |
| From reading the
paragraph in "How to Run a Lathe" I see a contradiction between it
and your explanation. The paragraph (for those that do not have the
book) is as follows" The center indicator is used for accurately
centering work that has been laid out and center punched for
drilling and boring. The short end of the center indicator is placed
in the center punch mark (of the work-my addition) and the tail
stock center point is brought up close to the opposite end, as shown
in Fig. 153. For accurate work, the long end of the indicator (at
the tail stock center point-my addition) should remain stationary
when the lathe spindle is revolved. I can see Chris' confusion,
since mine is the same. Fig. 153 shows a dead center in the tail
stock and the long end of the center indicator in very close
proximity to it. There is what appears like a bushing at the end of
the tool holder that is in close proximity to the center punched
work. I think that, and the short end of the center indicator in the
center punch depression, is the only thing that holds the indicator.
As one rotates the lathe spindle, and I take it that is done by hand
or at a very slow speed, the long end of the indicator in proximity
to the tail stock dead center is watch for any movement from
coincidence. Correct me if I am wrong. Fred (5263) |
| Yes, you are
correct if they are using a centering indicator composed of a
ball-joint mounted rod in the tool-post. Really hard to see in the
picture -- have to study it for a long while to see the details. In
this case the far end of the indicator (near the tailstock center)
is indeed free to wiggle and does so amplifying the amount that the
pop mark is off center by the ratio of the lengths to the ball joint
(or 2-axis swivel). Much harder to make yourself than a
"between-centers" indicator rod (obviously), but can be used to
great precision w/o need for a DTI. Thanks for pointing out the
"fine print". Paul R. (5265) |
| The shaft
is going through a ball/gymbal sort of holder held in the toolpost.
You look for no wiggle on the far end. Using the tailstock center
for eyeballing is just a handy way to do it, if the cross slide is in
too far, the point of the indicator ends up on the far side of the
tailstock center, out too far it's on your side of the center. Makes
no difference in practice, The far end only wiggles if the point is
wiggling. The difference in length on either size amplifies the
woggle, a thou is hard to see, 5 thou is pretty easy. This sort of
indicator is pretty well unused any more, it's a holdover from the
days of test and dial indicators being terribly expensive. These
days it's cheaper to use an indicator and a length of 1/8 drill rod
with a point held in the tailstock. Still a very neat looking little
piece of gear, if I ever see one cheap in OK shape I'll probably
give in to temptation to buy and refurb it, just because it's cool.
Stan (5271) |
| The
explanation of a ball gimbale held by the tool post seems to make
sense when studying the photo. The amplification of the rod movement
at the tail stock center would be easy to see. Chris
(5277) |
| Layout Question |
| Question: What is
the most accurate method of center drilling both ends of a shaft
with offset? Say, a true center, and three centers at 120 degrees
1/2 inch from the center? (like an offset crankshaft). Clamping in a
fixture and marking with a scribe from a surface plate the best way?
(5906) |
| Keith You have most
of it but there was a special quick way to do it that either
Westbury or Geometer documented. Let me look around for it and I
will post it when I find it. JWE (5911) |
| Keith A good
question and there are several ways to do it. For me you must first
establish a true center and then divide the surface for the number
of offset throws you need. The attached article by Geometer from his
Beginners Workshop series shows one of the best methods of
establishing these lines. Once this has been done all you need then
is to set the stroke of each offset center. For this I recommend
first a surface plate, 2nd a V block that will accommodate the
material and most important of all an adjustable height gauge with
scriber. There are several around at reasonable prices or you can
make one from a caliper as has been illustrated many times in the
magazines. My recommendation would be a $60 dial height gauge from
say J L or IPS. Others have them as well. With this you would first
establish the scriber to the center height of the material resting
in the V block and then dial in half the desired stroke, rotate the
material until the desired line is vertical and pass the scriber
across to mark the center. Now rotate and mark the other locations
on the other throws. Next question are you just going to drill these
points or are you going to mount in the lathe and turn throws on
these centers. To know this is needed because there are different
ways depending on the final use how to do the next steps. And oh yes
mark out both ends or the bar at the same time that is why we have
the material clamped in the V block and are using a height gauge
because then it is simple to scribe both ends exactly the same at
the same time, saves multiple setups. JWE (5918) |
| For layout, I would
use offsets and work on a surface plate with a good set of known
matched V-blocks To simplify things, I would first use a 4 jaw or
collet in the lathe to center dimple one end. Just enough to resiter
center. Then with a sharp V-tool in the compound, move out to your
desired radius and scribe the diameter on the faced end, turning the
lathe by hand. Don't change this setting (note dial readings). Turn
the part around, dial it in again, center dimple, and again advance
the carriage to scribe a circle, exactly the same as the other end.
Now remove the part from the lathe and clamp it to the matched V-
blocks (or only one if it is short) To get the top throw, use a
precision square or knee, line it up with center and scribe straight
up through your scribed diameter circle. To get the bottom 2 throws,
which will be at the same height, but below center, use the
following formula (this is only for 3 equal throws) x/R=sin30§, or
Equivalently, x=Rsin30§ "x" is the distance below center you need to
find, R is your known radius, sin30 is on your calculator. Find
sin30§ on a calculator, multiply it by your known radius; this
equals x, the height _below_ center. Set an adjustable parallel, or
a height gage, or a planer gage to exactly center height on the part
as it sets in the V-block(s). Now deduct the value "x" computed
above. If using an adjustable parallel, mic it at center height,
deduct the "x" value on your mic, screwing it down to the new value,
lock the mic, and refit the parallel to it. Set the parallel flat on
the surface plate against the end of the part, and scribe through the
previously scribed circle. It will intersect at 2 points, one to the
right and one to the left, the location of both of the other throws.
This is a very exact way to do it, but on small parts, layout error
can be large, You do need a good eye, and good procedures. The
technique itself is simple. If I were making the part myself, I
would dispense with layout and use machine elements to center drill
directly. One way that occurs to me would be to use a spin index or
dividing head, and clamp it to the cross-slide, lined up with the bed
axis. The lathe and index center heights do not have to match, but
must be within the offset distance required on the part. I would
face and center drill both ends "the usual way", and step out the
required distance using the crosslide and a sharp V tool to scribe
the circle for the crank throw off set as above. Next, transferring
the part to V block(s) on a surface plate, scribe a line at exactly
center height on both ends and one side. The side is optional, but
will make it easier to keep track later. work closely, because when
the part is swapped end for end later, it doubles the error.
Transfer the part to the index and set the index on 0. Leave the
collet or chuck snug, but loose enough to be able to twist the part
with some pressure. Put a clean sharp center in the headstock chuck,
collet, or taper. Use the cross-slide to position the index until the
enter point intersects the throw circle. Now twist the part in the
index collet or chuck until the scribed line lines up with the
center point. Again, be precise and sure. Lock the index collet or
chuck and check once more. Lock the cross-slide, if you can. Change
the headstock center for a center drill. Using the carriage, advance
and drill the hole, then index 120§ on the index and drill the next,
etc. Index back to O, turn the part around in the index and be sure
to line the scribe mark up on the same side as before. (this is what
the scribed line on the side is for). Adjust the part by twisting it
is the index until the scribed line on the end again is dead center
on a clean sharp center in the spindle nose. Tighten the index
collet or chuck, replace the spindle nose center with a center
drill, and proceed as above. I have considered a worse case scenario
above where the part is "longish" but might not fit clear through
the index. If the part is long enough to fit clear through the
index, you can drill your first set of holes on one end to accept
dowels. When the part is swapped around to do the other end, you can
indicate to the dowels (the part is sticking out the back the index)
or use a previously arranged positive stop set up to locate the part
by means of the dowels. What are you making? Smt (5930) |
| There are a number
of ways to approach this, how big is the part, what size is the
circle ( is it on one or both ends, must the holes be collinear or
not) and what do you have to work with? although the easiest way
might turn out to be the fixture - what do you have to build it from
and how many times do you have to do this operation - is it worth
building a special fixture for one part? (5940) |
| I'm building a three throw crankshaft 120 degrees. It's
also about 60% a learning experience,,, 40% real broken tooling and
a bunch of poor performing steel wool leftovers. At 09:34 PM 8/22/02
+0000, you wrote: That was the thoughts at first,,, that was going
to be the only "real" measurement I had to make. I guess that brings
up the question,,, assuming again,,, that the person doing this is
skilled,,, is it more accurate and reproducible to locate the offset
centers by measuring with a height gage, or dividing the inscribed
circle with calipers? It seemed to me,,, with the cylinder in a v
block on a surface plate and centers located and marked,,, the only
real measurement that needed to be transferred was the radius value
to calipers. The other need was a transfer line,,, vertical or
horizontal going thru the center, the same on each end. That could
be done with a scribe or square from the surface plate. The angle of
the throws using a height gauge depends on the center height above
the surface plate, and the radius of the circle. Errors in these
measurements would affect the angle and throw of the journals. The
angle of the throws using a division of the circle is independent of
the center height or diameter. Just depends on the eyeball
resolution dividing the circle. Shouldn't be any worse than trying
to mark the circle from a height gauge. Errors in measurement would
just affect the throw of the journals. Humph,,,, I'm out of my
league. I need to go hack up some aluminum and make a few scratches
so I can see what it is I'm looking at. Now having said all that,,,
I bet all things considered,,, I'd be better off doing the height
gauge than doing the division of circumference in relation to a
witness line. I guess It would be cheating to just clamp the sucker
in a piece of hex, that would sort of ruin the learning side of
the gig.
(5945) |
| When I machine
I get this |
| When I turn some
thing down I always get these lines in the part I machine. It does
not come out smooth. I have used new tools re-sharpened ones etc. What
is wrong. I need a smooth finish.
(6068) |
| You more than
likely need to change out one of the change gears to slow it down. I
can not tell you which combination, I have been trying to figure
that out myself. For some reason no one seems to be able to answer
that one, and I can not figure out it from the diagrams on the
cover. It looks like to me all it gives is combinations for thread
cutting. So far I have net got a smooth cut either. Clint (6069) |
| Dear Auntie Dodo,
...gotta be careful how I spell that one! If your looking for a
precision finish that is also to dimension try this pine and stick a
piece of 200 grit wet or dry silicon carbide sandpaper on it. You
can either use contact adhesive or PSA paper. The piece of wood
should be slightly larger then your part. It can be made by drilling
a 2X4 with a hole-saw. Just use half of the hole ( Attach the block
to your tool holder using screws tapped into a piece of CRS that
slips through the tool post holder. Set the long feed for a fast
pass. Use diesel for a cutting fluid. Turn on the lathe, put some
light pressure on the piece as you engage the feed. Kinda like
knarling with very light pressure. Check your progress with a
mic. Some guys make a more elaborate set-up using a roll of fine sil/con
that can be advanced after each cut. This is the poor mans OD
grinding. It takes off less material and may leave a better finish.
Ron
(6070) |
| Here is the deal
on screw cutting feeds to feed rates. Threads per inch divided by
1.0 equals your feed rate in thousandths per rev. Or you can
calculate it from the ratios. If you can figure ratios you can
figure feed rate. ratios are number of teeth / number of teeth= gear
ratio. Ratio X ratio until you get the final drive ratio. FD
divided by lead screw pitch(ie.125") (or 8 threads per inch lead
screw)= feed in .001" took me a little while while to figure out
this formula but it works for C type lathes that feed of the half
nut. for good finishes you need to feed at about .005" or less at
higher then normal speeds for the diameter. this is a generic rule
though. Kerry (6079) |
| Clint (and
antiedodo) I think you are really asking two questions. The first
question is "how do I get good surface finish?. Especially for many
amateur machinists cutting steel, this seems to be on a par with
determining the meaning of life. There is a long list of aspects to
consider, like cutting tool profile (relief angles, clearance
angles, tip radius, etc), tool sharpness, cutting speeds, feed rate,
depth of cut, lubricant, etc. There are lots of books which will
help here, at least in terms of the basics, but in general good
finish comes with larger tip radii, perfect tool sharpness and fine
feed rates (after the basics are covered, like tool angles and
cutting lubricants). The part of all this affected by the gear train
is the feed rate, typically expressed in thousandths of an inch of
feed per revolution of the workpiece. For good surface finish you
want to be in the range of a few thousandths of an inch per
revolution. For lathes with power feed in the apron, the apron
typically has additional gear reduction, as well as taking the feed
from a keyway in the leadscrew rather than using half-nuts. On a
typical lathe of this type, a leadscrew speed corresponding to 160
TPI (i.e. a thread pitch of .00625") feeds the carriage about .002"
per revolution when using the longitudinal feed arrangement rather
than the half-nuts (that is, about another factor of 3 in speed
reduction). I think your lathe, Clint, is a Type C, which as I
understand it has only half-nuts in the apron. As such you need to
use the gear train to slow down the leadscrew until it moves perhaps
.002" to .005" per workpiece revolution. Since the leadscrew has 8
TPI (i.e. 0.125"/revolution) you need a total gear reduction of
about 25-60. "How to Run a Lathe", at least my 1950 copy, shows gear
setups for a Type C which fit this category. If you don't have a
copy, by all means get one, not only for this but for many of other
aspects. The pictures show a triple reduction arrangement for all
these feed rates. For .0021"/rev, they show a 16 tooth stud gear
driving a 54/18 tooth double gear (causing the 1st reduction of
16/54), the 18 tooth gear on the latter drives a 72/18 tooth gear
(yielding the 2nd reduction of 18/72), and the 18 tooth gear of this
double gear drives an 80 tooth screw gear (for the 3rd reduction of
18/80). For other nearby feed rates (up to 0.0063") the overall
arrangement is the same, with different stud gears. I think you will
need the picture to see how they all go together. It is the same
picture as is on the chart on the gear cover, if you have that.
Frank
(6104) |
| Frank, this
is something like what I was asking, what gear arrangement are most
using for just a finish in general, I do understand what you say,
there is a lot of variables, and different arrangements. I thought
maybe there was a general arrangement to get a little practice in
and then go from there. My cover has 3 pictures. Clint (6108) |
| Clint The picture
of the Type C index chart in the 1950 edition of "How to Run a
Lathe" shows 4 different arrangements (in figures 1-4). #1 shows a
"speed multiplier", where the leadscrew turns faster than the
spindle, using the 18/72 gear with the 18 tooth driven (by an idler
gear from the stud gear). #2 shows the stud gear "directly" driving
the screw gear (via an idler, which doesn't change the ratio). You
get one level of reduction, with a ratio equal to the stud gear
tooth count over the screw gear tooth count. the 3rd figure shows a
two level reduction, with the stud gear driving the 72 tooth gear of
the 72/18 pair, and the 18 tooth driving the screw gear (again
through an idler gear which doesn't change the ratio). The 4th
figure is the triple reduction I described last time. It sounds like
your index chart doesn't have the last one. Tony's site
www.lathes.co.uk
has a photo of the 4 figure chart. Do you have a 54/18 double gear,
as well as a 72/18 double gear? If so I think you can set up the 4th
configuration (for very fine threads, or fine longitudinal feeds).
If not, the finest feeds you can do (with Figure 3) is .0083" per
revolution. With a large cutting tool tip radius that should still
give you a reasonably decent finish, if you have everything else
under control. You can also practice manually feeding the carriage
extremely slowly and smoothly, to start to get a feel for
everything else (like speeds, depth of cut, cutting tool geometry,
etc). Frank (6109) |
| Frank That clears
things up for me, I was mistaken, I have 4 pics, See I was unclear
because I assumed the first pic was for the finest feed. it all
makes since to me now. I think I do have the 54 tooth, but will have
to go through my gears to see I am converting my second SB 9" to a
QC gear box, I assume that It also has a setting for the fine feeds.
I think this lathe will be a good machine to spend the money on, I
already have the QC box, power cross feed for both, the ways are
nice, headstock is good. All I need is a the drive brackets and
pulleys, a tail stock, and I still am looking for the Mod C lead
screw, to cut a keyway for the crossfeed, and then a MOD A leadscrew
for the conversion on the other. I have a heavy 10 carriage ( Power
cross feed) that is in good condition that I am willing to do some
trading, also will have some other 9" parts extra. Clint (6112) |
| Clint Just to make
sure, what you need is a mated pair of gears, 54 and 18 tooth, which
turns freely on an arbor. I don't know if the standard set may also
have a 54 tooth screw gear (with a keyway). I expect that with the
QC gearbox and A/B type carriage (with power feeds), fine feeds get
easier, due to the further gear reduction internal to the apron.
Actually, if you get the power feed carriage on, the gearing gets
easier, even if you haven't got the QC gearbox on yet. Frank (6113) |
| Disc facing |
| Another way of
doing this is to bolt the disc to a face plate with some spacers of
the same width behind it. Either use some drilled holes on the
flange over the 5 inch diameter or some clamps. Bore and face the
part. The diameter of the beginning plate would probably have to be
a bit larger, say 6 inch diameter for it to be faced, so you
wouldn't have a parting line on the face. Then bore and face the
part. Next ,and don't remove the clamps just yet. Clamp the disc to
the face plate with another clamp, with a draw bolt through the
spindle bore. When this is done then you can undo the outer clamps
and turn the OD. It would also depend on how many you were going to
do. You could make an outer rim and a step on the disk itself. The
outer rim would have a bore to slip over the diameter you would turn
on the disk, say 5.125 or so, then with a bore in its back to clear
the OD of the stock of the disk. Hope this helps. Also, you could
put some bolts in the face plate and face them to have something to
space out the part from the face plate. Still be carefully where you
but the clamps. I would but them on the area close to the spacers or
you might warp the disk. Also, the disk will remain concentric if
you keep the out clamp tight till you get the bore clamp on. Tom
(6250) |
| Black finishes |
| Good question
Mario, When I complete a tool I usually degrease it in a solvent
like alcohol to remove dirt and fingerprints. Tie on some bailing
wire that has a loop on it for retrieving. Then either put it on the
stove gas ring or in the wood stove. If I don't care to harden it,
I'll let it go to a dull cherry. Then remove it and dunk it into a
bucket of cold 30wt. motor oil. Use the kitchen stove top for small
stuff. For big stuff, I put a piece boiler-plate on top of the coals
to keep the tool out of the ash. In your case charcoal will do fine.
It can be used to heat-treat as well as anneal and color. A small 5
gal. garbage can, (metal of course!) with a lid and expanded screen
double-bottom; along with 2 vents will do fine. We can design a
coloring chamber from this later if you want. Now if all you want is
a rainbow finish instead of black put the piece on a fire brick and
dance a large hot flame over it until you achieve the desired look.
If you want to do an 'apartment-finish', buy enough 'Perma-blue' to
cover the object in a glass vessel. Be sure you pre-clean it to
remove every bit of oil, dirt, and above all finger-prints! Put it in
the drink and leave it there for a day before checking it.
Professional gunsmiths will have an exhaust hood over the vat so
they can heat the brew to accelerate the process. You can do this
only if you have the proper equipment and can do this OUTSIDE. You
will have an odor to deal with so I hope any house-mates like the
smell of 'Ode To Forge'! regards, Ron
(6297) |
| Anybody have a good
recipe for blackening brass parts? I think there used to be a
selenium solution that gave a brown color. MSC sells some stuff -
two part product Anybody tried it? Frank
(6298) |
| Any of those
finishes you fellas been talking about work on aluminum? Or know of
some easy anodizing method for the home shop? Thanks for the
response on my turning question earlier this week. Alphawolf45
(6299) |
| Frank
this suggestion that I have for you to try is not what you're after
but it is interesting science and if you putter with brass often
enough it could prove useful to you sometime. I used to restore
antique radios and often got an old radio that some fool had put a
buff shine on the brass dial covers or other trim parts. To age the
brass ( sort of a controlled tarnish), I would suspend the part over
a bowl of ammonia and let the fumes turn the brass black. Don't like
the look? Soak the part in the ammonia and it will return to the
original finish. Weird huh? Alphawolf45
(6302) |
| Ron, That
sounds like fun! For my purposes, the oil quench will probably do
just fine. I have an old smoker that I don't use; it might be just
the ticket for a coloring chamber. Do you have any references as to
where I might read a little more about these processes? By the way,
I'm not familiar with the technical term "apartment finish"!?
Mario (6303) |
| Ron Newman
wrote the definitive online guide to anodizing here:
http://www.focuser.com/atm/anodize/anodize.html
A friend of mine followed his instructions and has turned out some
beautiful work. He did a few of my parts too and they look great. c (6304) |
| Corey The
anodizing instructions look very comprehensive. I will need to be a
bit more rested to read and comprehend the instructions but i thank
you for the link. Alphawolf 45
(6307) |
| Turning
question |
| I have had a lathe
for a lot of years now but I am still learning. Yesterday i was
making the threaded center for a backplate for my largest lathe , a
20 by 52" capacity machine. Point is that I was working a big piece
of steel and removing most of it with the lathe. Does anybody on
this list who uses high speed steel bits with their lathe , grind
chip breakers into their bits? I have never had any luck with that
and yesterday was one damn long day of dealing with long razor sharp
stands of hot shavings. Even when boring out the center of the
workpiece I had to stop frequently and remove the tangle that
wrapped around the cutter. I use carbide a lot when milling but
haven't had much experience of carbide at the lathe and never had a
chipbreaker on the carbide when i did use it. Okay what's the
secret? Alphawolf45 (6271) |
| It sounds
to me as though the "secret" in this case is the material. Most of
my carbide inserts have chipbreakers, and I've occasionally used a
small stone in a Dremmel to play around with putting a chipbreaker
on some M2 tools. I've never found a real solution to long swarf,
but here are some things I do that either help, or make the job a
bit more tolerable. Not pleasant, but a tad less irksome. Reducing
the top rake and side clearance can help sometimes, but as the
included angle of the cutting edge goes bigger, the finish quality
gets worse and the power and rigidity required from the lathe
increase. I have a roughing tool with only 2 degrees of rake and
about 3 degrees of side clearance, just enough to bite. The finish
is pretty poor, but the swarf does tend to break a bit more than
with a standard tool. You need to do the finishing passes with a
tool ground normally, but at least it helps sometimes. In most
cases, steels generate springy lengths of swarf rather than chips.
Leaded steels don't do this, but most of the steels I cut do. The
swarf "springs" may break when they get 6 to 8 inches long with some
steels such as drill rod, while other steels will just keep making a
chip that's 12 or more feet long. Depth of cut has a bit to do with
this as does the rate of cutting. If you cut drill rod deep with a
thick chip at low RPM, you can make a lightly blued spring that
won't break for anything, it's staying in one piece until you stop
the cut. Swarf from fine fast passes seem to break into much smaller
pieces, either due to the surface roughness of the stock creating
stress risers in the swarf, or perhaps the drill rod swarf is
cooling fast enough in free air to harden to the point it breaks
easily. The thicker the chip, the less it wants to break. When I run
into a steel that just plain won't break the chip, I either make
sets of cuts into the stock, maybe an inch or so apart, to around
the final depth, so the cut becomes interrupted as the power feed
advances the cutter past these gaps, or flip the power feed off when
the length is getting silly long or dangerous, just to break the
chip. I got the idea of toggling the power feed from the peck
drilling feature available on some higher end mills and radial
drills. You do get a disruption in the cut each time you stop the
power feed, so the final pass or two needs to be done in one
continuous cut if this isn't acceptable for the job. Some steels
will let you break the swarf with a chip hook. When boring a
material that behaves this way, I often cut the bore to almost final
ID in steps maybe 1/4 inch into the work at a time, then do the
final bore to size down the entire bore. This way you have more room
for swarf to make its way out past the cutter rather than tangling
and packing around the boring bar. If it's any consolation, I've
sure had to untangle more than one boring bar myself. The deeper the
bore the more it tangles. Not fun. This is one of those pain in the
rear issues the books don't seem to talk about, they seem to always
say "Just look at the lovely continuous cut, with the smoking hot
swarf curling nicely off the tool!". I think the caption writers
have never done a 2 foot pass on a mild steel shaft, or if they have
they've always worked in shops with large open floor area so clean
up isn't a hassle. If they have even been flailed by one of these
beasties getting snagged by the chuck, with the length of swarf
spinning around throwing off bits in all directions they seem to
remain quiet on the issue. I sure don't see anything lovely about a
15 foot length of springy razor edged swarf, particularly when
working anywhere near the chuck. It's one of the few things about
machining that I actually find zero pleasure in. Sounds like we
share our failure to appreciate this particular form of beauty. Stan (6274) |
| I switched to a
Kenametal 5/16" shank tool bit holder with a T221S insert and
corrected about 75% of my long swarth problems and does a lovely
finish. My 5/16 Kennametal boring bar with the TPMT 2151 insert also
breaks a lot of the swarf. The boring bar is hollow so when I do any
amount of boring I hook up my luber pump to the back end of the
boring bar and I run another luber hose off a tee to run coolant
over the outside of whatever I'm boring. Seems if you keep the heat
down you get more chips and less tangled swarf and it stops the case
hardening effect especially in turning stainless steel. I make
stainless blow pipes for the glass blowing industry and have to
drill a 3/8" hole through pieces of 1"x 8 3/4", 309 stainless. If
you let it get hot just once you've had the green weenie as it
instantly hardens and you've had the bun. (6278) |
| A few other things
to try are taking a deeper cut and try different feed rate and
speeds. Generally a deeper cut and a faster feed rate. You will just
have to see what your setup can handle. Also, make sure the tool
center height is correct, especially with ID tooling. Also, with
long B-Bars, they get drugged down off the center line. You might
try and set the tool nose a bit above center line and see if it
helps. I really haven't used this for ID tooling, but mainly for
cutoff tooling. Just giving you some things to try. I would say to
try the coolant. Get a spray bottle and mix some up. If you don't
have a coolant solution, try soapy water. Its been more than a few
year since I've used HSS tool bits. The inserts make life so much
easier. Still, many of the newer machinist just don't develop the
touch to grind tooling for odd forms or radii. The way I was taught
to grind a chip breaker was to have the bit at say a 30 degree angle
to the grinding wheel with one of the side corners or the bit
pointing up. (or say the flats 45 degrees from horizontal or
vertical). Grind the total face (front) of the bit at this angle
(you could say compound angle). There should be a point essentially
on the upper left corner now. You will relieve the left side, say 5
to 7 degrees. Next with the corner of the wheel, grind a gouge
across the top. Deepen the gouge and advance it till it just starts
to make a sharp edge, with the angled front or end face of the tool
bit. The tool should be done now. Maybe sharpen the edges with a
stone. Not exactly the best instructions, but its the best I can
explain. It more of a visual thing. Tom (6279) |
| Vibe trail? |
| My SBL 10 seems to leave a very pronounced finish,
/////////// across any shaft. What is causing this? The slant
pattern suggests some kind of vibration but I'll be dammed if I can
find it. Probably something very simple right under my nose. TODAY'S
BONE HEAD SHOP TIP: Want to do some real quick diameter layout but
don't want to use layout dye? If your doing face work and want to
skin down some diameters, just put your 6" scale on the tip of your
tool and watch the scale as the facing commences to your desired O.D.
When you get close to the diameter, just stop a bit short for some
clean-up. This works real good, tried it yesterday. Ron
(6597) |
| Ron, It might be a
resonance of the belt drive. I'm not sure of any real cure. Maybe
one of those link type belts. They claim to reduce the vibration.
Sometimes I'd take a piece of wood and press it to the part. This
would help reduce the vibrations. Also, o-rings on the part
sometimes reduces the vibrations. I am taking it that your lathe it
tight etc. I wouldn't expect anything less from you. I did have this
problem with some lathe at school more than a few years back. They
were Enterprise lathes from India. These lathes were silk smooth,
but had a vibration problem on longer parts. It made doing barrel
work about impossible. I was one of the few who used these lathes.
From what I understand, the belt adjustment was a problem with these
lathes. Tom (6598) |
| How on Earth could
an O-ring reduce vibration? I've heard this before, but the physics
escapes me. Flash (6600) |
| More information
please. Power feed? What pitch between marks? What pitch have you
selected for feed? Describe your cutting tool, is the tip of a
smaller diameter than the feed pitch? If you put your hand on the
carriage during feed can you feel a cyclical motion at the same rate
as the rotation of the leadscrew? Just a few ideas. Anthony
(6601) |
| Damping. David
(6602) |
| Vibration is the key to solving the problem. I used to
do vibration analysis on large rotating equipment, with a vibration
analyzer. You have a graphic vibration analysis on the work piece. Try
to find what rotating component if the lathe that pattern
corresponds to. RC (6603) |
| Ron, I'm sure
you have check the following: Headstock Bearing Clearance, Belt
Tension, Motor bearings, Does the lathe have a sheet metal base or
the cast iron base? Sheet metal will resonate more. Does the pattern
happen only in back gear? Back gear clearance may be off. Is the
cone pulley loose on the spindle? This can cause finish problems in
direct drive. Is the rear saddle gib too loose? Is the headstock
bolted down tight to the bed? Does the pattern only happen at a
particular feed rate or R.P.M. (i.e. Surface Feet Per Minute)? Is
the tool bit properly ground and sharp? I know that you are an
experienced lathe operator but for the benefit of those who may be
having the same problem, I listed these most likely sources of
vibration and surface finish problems. Webb (6604) |
| I have a vintage
1952 SB light-10 lathe, which I have cleaned up after an interval
(15-20 years) of storage in a closed-out high school shop. It seems
practically new after clean-up and paint (get some original paint
from SB and then you only have to paint what needs it} but noise and
vibration from the underdrive cabinet was terrible. After long
periods of storage, the v-belt takes a strong set and causes a
strong vibration. I installed a segmented belt, which set up a
terrific growling noise. You should know that the initial drive uses
oversized pulleys (5/8" across the belt), so the segmented belt
contacts the bottom of the groove, instead of the sides of the
pulley. A fresh belt of the proper width (type 5?) killed most of
the vibration. I also padded the motor mounts with rubber washers,
which also helped. Over tightening the motor mount bolts will bring
the resonance of the motor back, though. Padding the interior of the
cabinet with Dynamat (used by the teens to line their superwoofer
enclosures-standard disclaimer) helped much less than the new belt.
H. J. (6605) |
| I believe that the
idea is that it changes the mass of the part slightly, which changes
its resonant frequency. Resonance only occurs at a specific
frequency and its multiples for a given part. For example, if you
have an out of balance wheel on your car, you might get a vibration
at 30mph. But you would also get a vibration at 60 and 90mph since
they are multiples. 31 mph should be enough to stop or reduce the
vibration. If you are experiencing resonance while turning a part at
240 rpm, and you add mass (i.e. o-rings, wood etc). It may bring the
resonance frequency to 239 rpm, which although it is a small change,
it should be enough to make the problem go away. C (6606) |
| Flash; Change of
mass and damping, with damping being the main mechanism. This is the
similar to the standard practice of wrapping a brake drum with a
rubber band (a big one!) prior to turning on a brake lathe. On a
brake lathe, the band may be weighted with lead, or simply be a
thick band of rubber. Localized damping also tends to break up
harmonic oscillations. While chatter is an oscillation, you may have
had occasion to try to kill chatter and suddenly had the entire
shaft start to go nuts rather than just squeal. In automotive
applications, some front wheel drive half shafts have a rubber disk
secured to the axle to provide damping. This won't stop all
vibration, it just helps keep it in control so the axle doesn't
start to whip or hammer the CV joint bearings. Stan (6607) |
| Phooey. The mass of
an O-ring is trivial. How does it achieve "damping"? Where is it
placed to do this? Both the tool and the work piece are many times
the mass of an O-ring and exert forces orders of magnitude more than
an O-ring could. As I said, the physics of it escapes me. (6624) |
| I clearly do not
understand what takes place during damping. Can you enlighten me?
Flash (6625) |
| The mass of the
work piece decreases as the operation proceeds, changing
(increasing) the resonant frequency continuously. I think the
phenomenon is something else. Flash (6626) |
| There are several
factors at work in a "singing" workpiece, and the more complex the
shape the more complex the vibration pattern. We can drag out the
differential equations and analyze every one of those modes if you
wish, but more complex shapes would need a Cray to solve them. Even
a simple shape like a long slender rod has waves running
longitudinally up and down its length as well as radially, so
damping approaches get impossibly difficult to quantify. We probably
ought to assume for simplicity we are not talking about chattering,
which is a much lower frequency movement of the cutting system and
has more to do with toolpost and workpiece rigidity, elasticity, and
mass than audible singing that leaves vibration patterns on the
work. Damping with an O-ring, rubber band, or with your fingers
works beautifully, as others have said. (Yes, even the renowned late
teenut (Robert Bastow) on RCM spoke of using this bare arm, bare
finger holding technique at times, though I would never personally
do such a dangerous thing, myself. I would never do anything that
OSHA says might harm my delicate bod, since they are my heroes and I
always support everything they say. I even post MSDS sheets on the
wall of my garage.) :-) I agree with Flash that mass would at first
blush seem an unlikely major contributor, but it turns out to have
something to do with reducing both amplitude and frequency of
vibration. If you were to try the finger approach on a lubricated
slender rod - against all reason - I have been led to believe that
it takes very little pressure pinching the rod between thumb and
index finger for the "singing" to reduce or stop. Since one's skin
has very little mass, that suggests a different physics at work, at
least in part. Don't forget that the vibration can originate partly
in the tool bit and its holding system, which has sound waves
running up and down its length as well. One clue to what's going on
might be derived from watching someone play a violin - if you play a
note on the open string and then just *barely* touch the string
(which is certainly a long slender rod) at the right point, the note
becomes several octaves higher. If you press harder, the frequency
drops back to a single octave above the fundamental. Without getting
into the math, it turns out that extremely tiny changes in the
vibrating system can damp out or change the fundamental drastically.
Some of the effect is caused by mass, some by tension, and some by
the point of application of the damping. The point of this much too
long winded discussion is that when you are talking about traveling
wave effects, you are dealing with forces that have nothing to do
with the large tool-to-workpiece force that Flash mentioned below,
and can be much smaller to produce a large effect. If anyone is
interested in learning more, you might want to borrow a first year
college physics book and turn to the section on Sound. You'll
generally get a good discussion of fundamentals without a lot of
heavy math at the beginning. And that's enough philosophy for now.
Mike (6627) |
| Think more of
it as a shock absorber, soaking up the energy that would just
continue to otherwise build. (6628) |
| Concur in spades, LaPlace and s-domain aside, there are probably no less than 20 to 30
resilient pieces ( probably more) and as many contact gaps, one
driver ( motor-which provides both shaft torque and housing
vibration) and more friction forces than I could guess. the real
point is - there are most likely only a very few places this problem
originates and it's most often that it is somewhere in the drive
train close to the motor and its reduction unit and vibration
controls. generally, this kind of stuff can be found once you make
it start - use a mechanics stethoscope ( or make a cheater if you
like) and hunt down where it is loudest in the fixed parts and
housings. there is where you need to look to dampen or avoid it. a
very small change there could defeat it entirely as the evidence on
the workpiece is the result of STORED energy in the mechanical
system not being released or transmitted smoothly. the damping
change does NOT have to absorb all of the energy, just change the
harmonic response characteristic enough to remove the storage
phenomenon. (6629) |
| Trying to keep the
complex simple :-] It is significant that the damping instrument in
all the examples is not rigid, does not itself participate in
resonant behavior. You have made me think that the effect seen here
is a result of standing waves and therefore could be dramatically
effected by the most trivial absorption of energy. One last
question. Is the pattern that is produced on the piece very shallow
and absolutely regular? Flash (6631) |
| I believe you
understand the essence of it. pjwizr_99 said it better than I did,
and the use of a stethoscope is an absolutely brilliant idea. I've
filed that away for later contemplation. It's worth noting that some
lathes, like my Hardinge HLV-H, go to unusual lengths to keep
vibration inducing mechanisms to a minimum. For turning and facing,
Hardinge uses a slow speed DC motor that drives gears directly in
the carriage. I've observed the whining gear train in the South Bend
Heavy 10 introduce some fascinating patterns - though slowing the
spindle speed usually helps that sort of thing. If you can feel
vibration on the headstock, then the pattern is being introduced by
that external excitation. -Flash- As pjwizr said, there are multiple
elements contributing their own resonant frequencies to the
mish-mash. What you get is a pretty good demonstration that Fourier
was right - with a depth measuring microscope you could probably
discover a fundamental frequency and all sorts of overtones in the
pattern, and they may well form a corkscrew pattern on the OD
depending on their contribution to the overall mix. The fundamental
may or may not have the greatest amplitude (depth) but since several
frequencies are present, there will usually be one that will have
the greatest amplitude, and of course it will be repetitive since it
is a sine wave. If you are asking if a given repetitive microscopic
depression could be parallel to the axis of the work piece, it would
to my mind be unusual - that would seem to be more of a vibration
from the toolpost system than workpiece vibration, though that would
probably require additional thought. Mike (6633) |
| And with a good
enough measuring instrument, you should be reconstruct and play back
what the machinist was muttering as he tried to deal with the
problem. Chris (6634) |
| Flash; A damping
material absorbs mechanical vibration and converts it to heat. As
the energy usually isn't very high, the heat produced is quite
small. Most damping materials will move, just not quickly. You can
stir thick oil with a flat paddle slowly, but if you try to move
fast, the energy required to produce the movement goes up quickly.
Add a little valving on the stick, move it up and down in a column
of oil, and you have a shock absorber. If you've ever installed
shocks, you know you can pull out the shock rod slowly, but if you
try to give it a fast tug it just won't move. Oil provides viscous
damping, rubber provides elastometric damping. In either case, the
idea is to make a spring (or in this case a system that can be
modeled as a spring) stop oscillating. If you're into electronics, a
bypass capacitor on a power supply line is the electronic equivalent
of mechanical damping. Yes, this is a gross simplification, but hey,
it's close enough for a high level view :-) You may have run into
this also when cutting some materials, a thick cutting oil and fresh
way oil on the carriage and dovetails may stop a chatter than won't
go away with any speed or depth of cut combination. There's a fairly
decent overview of vibration and damping at:
http://www.lordmpd.com/pdf/ia_theory.pdf
I don't recall all the previous responses you've received, but have
you: 1) Used way oil on the bed and carriage 2) Checked that your
gibs (cross slide and compound) are snug and oiled 3) verified that
the tool geometry is reasonably correct for the material 4)
minimized overhang and provided as much support for the work and
tool as possible? Usually one or more of these four steps will sort
it out, unless your headstock bearings are out of adjustment or
defective or the drive system is inducing the vibration. A flat spot
on a drive belt can really get things bouncing. Lantern toolposts
are particularly prone to oscillations if the tool is sticking way
out in air, creating a cantilever with the beam of forged steel
which loves to ring, and a long lever to apply to force to any
looseness in the support structure (compound and cross slide.) If
the compound travel is at an extreme limit, you also tend to find
more chatter. I try to set things up so the toolpost downward force
is carried straight down to the carriage, rather than having to zig
zag back and forth through the compound. Stan (6635) |
| It's not the mass
of the O ring that gives the damping effect but the energy absorbing
property of the rubber. If the O ring material is compressed and
then allowed to expand not all the energy is recovered. The rubber
gets slightly warm. The mass of the O ring will change the resonant
frequency. A simple example; wet your finger and rub the rim of a
clean glass, it will 'sing', put water into the glass and the note
will change. Put a rubber band around the glass below the rim and it
will not resonate. David (6640) |
| Vibration
problem |
| I guess that I am
not the only one having this problem. I have a 10K and have totally
rebuilt the apron, including boring and bushing the worm, worm gear
shaft and the hand wheel shaft. The handwheel shaft was to badly
worn and scored, that I had to machine it to .594 and ream a bushing
to size. I also made several piloted shell reamers to repair the
worm and wormgear bearings. If anyone is interested in doing this
(it is a real pain to do) I have photographed the reamers and
procedure in my mill. I also re-shimmed the headstock bushings and
adjusted the spindle endplay. None of this seem to fix the spiral
and other patterns that I get when I take a finish cut. My dear old
dad's 6in Craftsman lathe gives me a superb finish. If I can come up
with an answer to this very vexing problem, I will post it. tomd
(6616) |
| Are you
using the same tool for finishing as you're using for roughing? If
the tip diameter of the tool is less than the feed pitch you are, in
essence, cutting a fine pitch thread. Of course there are many other
potential sources of the problem, the only reason for mentioning the
above is that it's an easy problem to correct. Anthony
(6620) |
| Also the same
comment applies to depth of cut to where the depth of cut should be
greater than the tip radius of the cutting tool. JWE (6621) |
| I am using a tool with about a 1/16
radius and the feed set at .0018 in. per revolution. I have tried
other spindle speeds/feed rates and it just makes the pattern
different. (6622) |
| I came to the
conclusion that the only thing left that was causing the weird
pattern problem. I made a shaft that extends thru the spindle with a
3/8" machined end to fit my angle drill. I disconnected the spindle
from the belt drive (I have a bench model 10K with v-belt drives). I
engaged the feed to .002/rev. and turned the drill on at
approximately 1000 rpm. Eureka!!! the weird pattern disappeared. it
seems that the problem is caused by something in the belt drive
system. Will pursue this further next week. tomd (6623) |
| Just a thought but
is your chuck on the spindle tight with all its fixing screws done
up and the headstock bearing in reasonably adjustment and the bit
your working on not too long and thin etc? pp (6630) |
| Rings on
workpiece |
| Been playing with my newly installed QC box and
power-feed apron. Here's the deal: Turning a piece of stock about
3/4" OD middle backgear speed about 4" out from the chuck .008 cut
set up for the slowest feed possible [.0015] with an indexable
carbide cutter or with a HSS bit makes no diff compound and
cross-slide gibs locked down tight rear saddle gibs snug enough to
lightly drag the handwheel on manual traverse bed reshimmed so
there's no rocking of the saddle--sits on all 4 corners. I
think the tailstock end is floating until I get the bench
rebuilt... toolpost locked down tight change gears set loose enough
not to whine or bottom and tight enough not to clatter nice smooth
finish, but I get a pattern--every 1/8" or so the diameter of the
workpiece varies--min to max diff is about .009...like a stack of
wooden barrels i guess is how I'd describe it. playing with the
feeds changes the length of the barrels. is the tool perhaps loading
up and playing with the depth of cut? there's no chatter, no
grinding, no funny noises to speak of at all...it does it both with
a piece of 360 brass and with a piece of some sort of funny tool
steel my buddy laid on me going to a faster feed, like 224 tpi on
the halfnuts without the apron power feed, the problem either goes
away or the 'barrels' become so long it gets lost in the
bed-wear-taper shuffle. reversing the tumbler at the end of the cut
without changing tool depth it mows all the high spots on the
back-cut. that almost sounds like the carriage is still walking
around a little but doesn't explain the 'barrels' effect. what is
causing this? I checked the headstock, spindle slop is about .0015
so I hope it's not feedscrew-drive gears worn out of round going in
and out of phase and loading and unloading the spindle. Seems to me
that'd only be a problem if the teeth were bottoming anyway. Is
there something about power-feed aprons that can cause this?
something in the geartrain inside the apron out of round loading and
unloading the saddle against the front way? it sure looks like the
effect of something going in and out of phase, but with the compound
and cross-feed gibs tight and the saddle gibs snug I'm lost. oh
yeah, I didn't mention with the same parameters and a much deeper
cut ['050] the finish isn't as good but the barrels effect isn't
there. the brass is a long piece of stock through the spindle and
supported by a live center in the tailstock [locked down tight with
the ram locked] the steel a short piece held in the chuck but also
supported by the tailstock...is too slow a feed somehow causing the
workpiece to flex like when you 'whip' one end of a rope laid across
the ground and watch the 'wave'? am I getting a torsional flex in
the bed itself with the tailstock end floating on the shims? lurch
(6925) |
| I
have the same problem with a Logan. I have replaced all the bearings
and rebushed everything to no avail. I have never figured it out yet.
although I suspect its in the V belts somehow even though I have
replaced them all. (6926) |
| The
usual noises of the thing running seem to fade in and out like an
airplane with the engines out of sync...and the timing on that does
somehow seem to correlate to the 'barrels'. I'll have to play with
it some more tomorrow and see what more I can observe. The only
things I can figure could possibly cause it are: 1] the
carriage/compound/tool post are somehow walking around or else 2]
the spindle is walking around or else 3] the workpiece is flexing or
else 4] the bed is flexing I wonder if there's some workpiece flex
happening at a frequency way, way too high or too low to hear? If
the workpiece is flexing that maybe could account for it. I'll have
to try some thicker stock and see if the problem is still there. I
don't recall ever seeing it on thick stock. I've got a piece of 3.5"
OD steel about 5" long, ought to be plenty stiff enough... Something
else I haven't tried yet--does your Logan do it turning between
centers or only with the chuck? If only with the chuck, is it only
when using the tailstock? If the tailstock is set too tight [ram
extended too far], would that cause workpiece flex? Does the problem
get worse as the workpiece heats up or as the headstock heats up?
This is a real puzzler, huh? (6927) |
| Several of us
touched on this subject a while back when discussing "patterns" on
the workpiece, but we were focusing on harmonic effects that leave
high frequency patterns of less than .001" depth in an otherwise
smooth finish, so the only reference made to your problem was in
passing. You mentioned an order of magnitude increase in the depth
of cut from the patterning discussed previously - a .009" delta in
OD is huge! I hate to drag out the old "your lathe is made of stiff
Jell-O" analogy again, but it sounds very much like that's the
fundamental basis of what you're describing. You've analyzed the
variables correctly below - everything forms part of a large spring
system whose spring constants are lower for smaller lathes, so all
those factors are elements in the problem. However, the place to
start working in my limited experience is the edge of the cutting
tool, and then work backwards down the chain of the spring system to
see where you might introduce some improvement. (This assumes the
spindle bearing clearance is set up correctly.) Normally, if your
tool face is cutting well, with the right coolant, you'll have a
beautifully smooth finish. If it's not, because of tool height,
clearance angles, tip radius, or attack angle, you will often get a
"digging in" every so often, frequently of the magnitude you
describe. It usually occurs on lighter cuts as you describe. What
appears to be happening is that the tool face doing the cutting gets
pushed away from the work against the spring of the lathe, cutting
less and less because of one or more of the factors above being
wrong. At some point, the spring system forces get to a point where
those forces are enough to overcome the "pushback" from the work,
and the tool quickly digs in back to the original cut depth. This
seems to occur especially with improper clearance angles on the tool
bit, a "ramp" angle on the tool (using a threading tool to do normal
turning, for example - the ramp on the left side forces the tool bit
away from the work with greater force than a tip with the cutting
edge perpendicular to the centerline of the work), a dull cutting
edge, or a cutting edge that is set too high or too low rather than
on the centerline of the work. Another point to look at is how the
tool tip "swings" on its pivot, again with the stiff
Jell-O concept
in mind. The Aloris type holders exacerbate this problem since the
tool is suspended to the left of the pivot point on the compound.
Push it away from the work and the tip describes an arc that digs
into the work when the push is removed. Put the tool on the right
side of the holder, and the arc is either tangential to or away from
the work, so you might try fiddling with that approach as well. This
is described in the South Bend "How to run a lathe" book, though
it's addressing the potential for the toolholder to slip (it's
figure 140 in my 50th Edition). The principle is the same, however.
There is often very little you can do to increase the rigidity of
your particular spring system, especially in a small lathe like the
9", so the only thing you can do is to work around the problem.
Assuming your tool bit is ground correctly (and I would be leery of
assuming a general purpose carbide insert is already ground to suit
your particular lathe - even though it may be fine on a larger one),
then increasing or decreasing the depth of cut or changing the
spindle speed or feed rate will usually help. I know this may seem
unsatisfying...it would be nice to be able to set up a cut of any
depth and any feed rate and have the finish come out the same.
However, the smaller the lathe, the more compromises you have to
simply accept as going with the territory, and work around the
limitations in other ways. Mike (6929) |
| Tried it
again and saw the depth of cut change as I leaned on the right rear
corner of the saddle...so the saddle was walking around. With a lot
of careful dorking around with the feed rate [faster], the rear
saddle gibs [tighter] and the saddle lock [ditto] I got it
resolved...but only when the aforementioned are snug enough it is
difficult to traverse the saddle by the pinion handwheel. Is it
normal to have to have things that tight? I'm thinking that's gotta
put a heck of a load on the leadscrew etc but I do note the thing
is almost silent under those conditions. This is a
piece-parted-built lathe; I'm wondering seriously if the bed itself
isn't wasp-waisted...or if each saddle has to be hand-fit to it's
respective bed? (6930) |
| Lurch, Try
moving the carriage front-and-back with your hands. This is what it
appears to be to me; front-to-back slop that straightens out on the
reverse cut. I don't think your workpiece is flexing, because
wouldn't you have the barrel effect on the reverse cut as well?
Reversing direction wouldn't cause the workpiece to stop
oscillating, IMHO. Bilal (6931) |
| That little tidbit was sort of crucial to any
analysis. If you've built up this lathe from bits and pieces, it's
important to make sure all the parts fit together. The original
lathes were machined with fair precision but not necessarily hand
scraped for fit, depending on the era. However, when you build up a
lathe from worn parts, you have a 50-50 chance that the parts wore
in the opposite direction from the part you eventually forced them
to mate to, quite possibly creating your situation. Before you can
expect to get any consistent performance out of the lathe, you're
going to have to run the measurements that Connelly describes in his
book, "Machine Tool Reconditioning". This process is not all that
difficult, but it will take patience and some Prussian Blue paste to
see where contact is lacking, as well as developing some scraping
skills. It is honestly beyond the brief interchanges possible on the
reflector group. Don't be discouraged by this - the process is
actually an enjoyable learning experience and will help immensely in
subsequent machining operations. Mike
(6932) |
| Great
minds think alike. As I read your post I just came in from hitting
every hardware store in town trying to find some Prussian Blue. My
toolmaker friend had suggested getting some Prussian Blue and fine
lapping compound and lapping the saddle to mate with the bed. Will
write back after I do the Prussian Blue, but I'm betting right now
the center-to-center on the ways is just a tenth or two off the
c-to-c on the saddle and hence the saddle is rocking. (6933) |
| You can get
Prussian Blue oil-based pigment at any art supply store. Get the
cheapest brand. It comes in tubes. Usually it is in a linseed-oil
base so it will dry and harden. Frank
(6935) |
| And
auto-parts stores. The local Sears Hardware used to carry it, right
next to the valve-grinding compound...now they have two hooks of
compound and no Prussian Blue. I had hoped that stopping at 3
different hardware stores would appease the '3-trip rule goddess'
and the tube I bought to do the valve job on the bike would turn up,
but to no avail. In the meantime, I put the original saddle back on
the lathe the one that came with it, with the horribly
wasp-waisted cross-slide dovetails and no room for the cross-feed
leadscrew power-feed splines and the old worn-out crossfeed
leadscrew and nut...and it doesn't rock on the bed, and the lathe
cuts true now [well, after I reset the tailstock setover but that's
another story I'll decline to tell because it's rooted in my own
stupidity and impatience], no 'barrels'... So I think I'll leave
this saddle on there and fit my power-cross-slide saddle and apron
to the 10K 4-foot bed I just nabbed for a hundred bucks. Less
danger of permanent damage from someday refacing the cross-slide
dovetails than from reworking the bedways. Lurch
(6937) |
| That is to
say it cuts more-or-less true on the halfnuts. There's still a
slight 'barrel' effect on the power feed through the apron but I'm
not worrying about that unless it's still there after I disassemble
the apron and clean and lube everything thoroughly. There's
definitely some binding action inside the apron itself. Even with
the apron sitting solid and NOT using the power feed, just the
halfnuts, the effect is still there to an extent though so there
has to be at least one more factor I have overlooked.
Frustrating. (6941) |
| How to cut
shims? |
| I need to
put new shims into the spindle bearing casting on my SB 10k. I have
never cut metal shim stock before - how do I cut it so as not to get
a burr or raised edge? Also, is it worth getting the peelable shims
used originally? Frank (7348) |
| I just
recently got some of the peelable shims from LeBlond for about $10
apiece...the 'peelable' aspect is nice, but they do require some
work. If I had to do it over again, although it would take time, I
would have a local machine shop surface-grind the original steel
shims on a magnetic chuck .001 at a time.
(7349) |
| Is it
possible to put the shim material between two matching well finished
edges and use a Swiss file to bring your shim to size? Phil
(7362) |
| As an
engineer I've done a fair amount of shimming (mainly in the dim
distant past!). It is not as fussy as some people seem to think -
really thin shim one uses decent scissors and thicker shim one uses
sharp tin-snips. To cut holes we used hollow punches, panel punches
(rarely) or even a chisel for thicker shim. A small sharp chisel is
also useful for awkward internal shapes and is used against a hard
surface - one can always re-sharpen the tools used. We usually then
tapped lightly around the shim edge with a light hammer for bur (if
any) removal. It's almost the same as making a gasket but one takes
care not to finish with raised edges. It may all sound a bit rough
but it gets the shim made and if care has been taken with the edges
of the finished shim I've never known a problem. Dave (7369) |
| Here is a
note that I sent to Frank at terranovapress Originally the shims
were as follows: 1. Aluminum thick shim 2. Peelable brass shims
(these suck!!) I made a new pair of aluminum shims that are .021
thick (this is and arbitrary thickness that I used, because I
happened to have the material) and lapped them so that they were
flat and parallel to .0002. I used 400 paper and measured them with
a .0001 micrometer. I can make you a set if you wish. I have an
assortment of plastic stock. that I then cut them with jewelers
snips. You could use a pair of manicure scissors. I have lots of
shim material and would be glad to send you some. I measured the gap
without the bolts, using feeler gages. I then placed a plastic shim
and the aluminum shims into the gap and torqued the bearing cap
screws to 33 lb/ft. Release and tighten the wedge bolts so that they
are just snug. Put the heaviest chuck that you have on the spindle
and use a 2 x 4 to raise the chuck/spindle to check to proper
clearance (.0005 to .001). I used a piece of bar stock to lift the
rear of the spindle. I assume that you have a suitable dial
indicator to measure this clearance. If you do not have an
indicator, I can loan you one. I mounted the indicator on a magnetic
base and clamped it to the cross slide with out the tool post. You
will probably have to do this a number of times to get the proper
clearance. DO NOT USE THE BOLT TIGHTNESS TO ACHIEVE THE PROPER
CLEARANCE. The plastic shim stock is designed to be used in this
manner. After you think that you have the proper clearance, re-tweak
wedge bolts so that they are just snug. As far as I can tell, their
main function is to prevent the bearings from rotating. Adjust the
thrust bearing to about .005 clearance. Run the lathe at high speed
and check the temperature of the bearings, using your finger. If the
get more than a little warm, you need to re-shim the bearing (s}.
Regarding the back gear problem, I have a spec. that came with my
parts manual, and will FAX it to you. If you want me to send you new
aluminum shims and shim stock, let me know and I will ship them to
you with the parts tomorrow. (7392) |
| Turning
plastics |
| I
thought this was just addressed, and searched the archives, but did
not see anything. what cutter geometry for turning plastic with hss
bits? same as steel? 5 deg side clearance, 61 deg cutter angle, 23
deg side rake, 5 deg front angle? do you set bit on center or above?
I am getting terrible finish, galled and scored with carbides. So I
figure on going old tech. dennis
(7883) |
| If you are
not doing precision work with plastics, you can use hand-held hss
tools used to turn wood. I find the scraper works well. I put the
tool holder parallel to the work and use it as a rest. Gives a nice
finish with, for example, Delrin. Frank
(7889) |
| I recommend
very sharp HSS tool bits with a bunch of clearance. Note that in
plastics, your tool bits will be very hot as the chip does not carry
much heat off the work. We do a bunch of work with nylon and TFE.
You might want to hone a small radius on the very tip of the bit.
You should have very good luck machining. Oinkle Tom (7891) |
| Vibration
Question from a newbie |
| I am the proud new
owner of a 9" Model C Lathe. My question is as follows: On my lathe
there is a motor with a V-belt pulley running a V-belt to a
jackshaft. The pulleys the V-belt ride on in the jackshaft are not
V-belt pulleys, but flat pulleys with no crown. The V-belt's bottom
ride on top of the pulleys. The rest of the jackshaft has 3-step
flat belt pulleys, with crown, that drive a flat synthetic belt to a
set of similar pulleys in the head stock. The motor is pivoted on on
side, and has a spring on the other, to the lathe bench. When I run
the lathe, the motor jumps up and down by about a 1/2", which I can
feel through the whole bench/lathe. It does not seem to affect the
surface finish I get, except on a heavy cut. On the other hand,
considering my skill at the moment, I could be totally mistaken. If
I could get a better finish, maybe it would show up. Where I really
notice it is drilling with the tailstock. The vibration seems to be
coming, not from the motor or jackshaft, but due to the V-belt. It
seems as 1 pass of the V-belt equals 1 peak in the vibration. Is
this normal, or do I have it hooked up wrong? Fred (8323) |
| Fred. What kind of shape is the V belt in? If there are any
cracks, separation or any signs of wear on the belt? Try replacing the
V belt. Also make sure you have the right tension on your flat belt. I
was having similar problems with vibration until I replaced the V
belt. Now I have minimized the vibration to almost nothing. Also be
sure that the motor and jackshaft assembly as with the lathe, are
firmly secured to your bench. Just one opinion. Congratulations on you
new ownership of the Southbend. Mine is also a model C. Bill
(8324) |
| Fred, I think
you answered your own question. It sounds like your v-belt has taken
a "set". Replace it and be troubled no more. They are also really
cheap and easy to change. There should be a size marked on the outer
periphery or you could just bring it to an auto parts store or to
Grainger. Good luck, Peter
(8325) |
| Fred, The
typical bench top set-up does not use a spring to the bench for belt
tension. There is an adjustable length rod that goes between the
headstock and the drive unit with a lever that pops over center.
These appear on eBay from time to time. Look for "belt tension
lever". I bought one from PKE in Libertyville, Illinois, but any of
the dealers mentioned on this list could probably help you. Glen
(8328) |
| On the setup
I have there is no lever, or place for a lever, between the
headstock and the jackshaft mount. Also, the motor does not mount on
the jackshaft assembly. The jackshaft assembly mounts via way of
three long slots to the bench. To tension, one pulls back on the
assembly and then tightens the bolts. The motor mount is two pieces.
One piece mounts on the bench and contains two pivot pins. The piece
that mounts on the motor has two U-shaped grooves that sit over the
two pins ( on the other half of the motor mount ). Tension is
applied mostly by the weight of the motor. The spring just keeps the
two pieces of the motor mount together. It all looks original. Tried
replacing the belt, no change. Fred (8338) |
| Fred. The
tension adjustment arm goes from the lever just behind the headstock
to the countershaft frame. This is a rod about 12-14 inches long with
a turnbuckle in between the two halves of the rod. You pull the lever
forward to release the tension on the flat belt to aid in speed
changes, and the lever is pushed back to lock position to tighten the
belt. If you don't have this, it is obviously missing. No way is a
spring going to give enough tension for satisfactory operation. Look
at some of the photos posted and look for a photo that shows the
rod. Maybe some of the more experienced owners on here can explain
this more clearly. Bill
(8339) |
| Fred. Look
at my photos named BillsSB9C,the last photo in my album. This photo
shows how the tension rod is fastened to the lever and countershaft
assembly. Bill
(8343) |
| That does not
look anything like the countershaft assembly on mine. I will see if
I can borrow a camera and post a picture tomorrow. Fred (8346) |
| Fixturing
question |
| I have a workpiece
.125" thick by 3.125 OD that I need to do some work on the face of
and I can't mar the OD which is polished finish. It's 6061. There
are two countersunk mounting holes in the face 180 degrees apart,
2.460 centers. I made a jig to hold it, looks like a steel mushroom.
Marked on either side of jaw #1 of the chuck to re-fixture the jig
in the chuck the same, and I can remove and replace it and it still
runs true. I spotted the holes in the jig by setting a scriber in
the toolpost with a piece of shim trapped between the scriber and a
dead center in the spindle taper, then backed it out half the center
distance of the holes to scribe a circle, then ran a line across the
center of the jig and put the mounting holes where the circle
intersects the line. 4 times I've done this. The jig is starting to
look like Swiss cheese. I can't seem to get the two mounting holes
accurately located. They always end up a little off. Where am I
going wrong? Is my drill press perhaps not accurate enough? Even
under magnification the holes look accurately located to the
lines...and I'm using the drill press spindle [turned by hand] to
start the tap straight [did I mention it's a new true spindle in the
drill press?]...but go to fixture the workpiece and it's out of true
about .030". Like, what am I missing that's totally obvious? |
| Lurch, Are you
starting the hole with a center drill or just a drill? Drill will
walk on you. If you center punch the mark, then start the hole with
a small drill (1/16), this might help. When you drill to size, then
other drill will follow the hole. Tom |
| My first thought is
to apply the KISS principal and just chuck the whole shebang in a
four jaw and indicate on the OD of the workpiece. That way you can
dial it in to perfect concentricity. All jigs end up looking like
Swiss cheese eventually, Lurch. :-) If you have a lot of parts to
do, is there any reason you can't put a shallow step in the face of
the jig to locate the workpiece on its OD? Then the clamping bolts
simply hold it on, rather than being required to perform relative
location duty as well. Actually, it sounds like a perfect job for a
step chuck to me. You have almost created one with the mushroom
fixture. Attached is a photo of one that should make you feel a
little better about your Swiss cheese. As to your layout problem, I
assume you compared the hole locations in the fixture with those in
the workpiece each step along the way (scribe, spot with a #1 center
drill, final drill, and tap), so at what point does it go awry? Taps
are notorious for shifting around, but I can't imagine it shifting
the hole center by .030" unless it was a pretty large tap and
asymmetrically worn, damaged, or poorly made. A tap is one tool
where it doesn't pay to buy imported goods. Mike |
| What about the
backlash in the crossfeed, did you come from behind the center to
get your starting point. RC a workpiece .125" thick by 3.125 OD that
I need to polished finish. 180 degrees either side and I with a
spindle scribe a mounting cheese. I always perhaps not accurately
located hand] to the drill about .030". |
| RC a workpiece
.125" thick by 3.125 OD that I need to polished finish. 180 degrees
I have pieces I have to accurately face that cannot be gripped on
their sides/edges. Have you considered a vacuum chuck? You could
tape the mounting holes, or design the chuck so vacuum is blocked
from them. Here is one I built, and use daily:
http://www.gearloose.com |
| I recall about 40
years ago seeing someone affix just such a piece to a faceplate
using flake shellac that was then heated and allowed to cool. It
formed a great bond that held well and easy to remove. Frank |
| I would worry about
this with 6061 Aluminum. The pieces might be made from a heat
treatment such as T-6. Aluminum, Brass, Copper and other metals age
harden. Applying heat to aluminum, will mess up its heat treatment.
It sounds like this is a precision part. One question would be what
type of screws are they? Are the hole from piece to piece the same?
Could the next size bolt smaller still clamp the part? Tom |
| Other than that the
job includes putting a bevel where face meets OD, no...I'm thinking
I'll just take the whole mess to work and use the vertical head on
the big Unimat with a coax indicator...trying to use the mounting
bolts [countersunk flatheads] to fixture requires exact
center-to-center and I think that's where it's going awry...time to
go to capscrews with soft washers and a plastic mallet for final
positioning… |
| I'm assuming your
"no" was referring back to my question below about the small step.
Since it doesn't need to be more than .030"-.060" deep, that would
leave you plenty of room for beveling the OD. I presumed you had
some work to do on the face that would preclude the use of cap
screws - but if not, obviously that's an easier way to go. Still not
sure why you were getting .030" shift in location - you might want
to figure that one out on general principles for "the next time..."
Mike |
| Why not hold your
"off center" jig in a 4 jaw chuck and true it up with the
independent jaws? Bill |
| Lurch writes: I spotted the holes
in the jig by setting a scriber in the toolpost with a piece of shim
trapped between the scriber and a dead center in the spindle taper,
then backed it out half the center distance of the holes to scribe a
circle, then ran a line across the center of the jig and put the
mounting holes where the circle intersects the line. --- --- Like,
what am I missing that's totally obvious? It sounds to me as if you
took up the feed screw clearance one way while trapping the shim
piece, then took up the feed screw clearance in the other direction
while backing it off to the radius of the mounting screws. If this
is the case, back the feed screw off at least one full turn beyond
the radius reading, then feed forward to the exact radius reading.
It would be best if, during this last forward feed and while you're
scribing the circle, you hold the slide back by some means in order
to keep all the slack on the one side of the motion. Also, lock the
slide you are *not* adjusting (either the cross slide or the top
slide). Does this help? Anthony |
| Could well be; I
can't honestly say...too much gone on since chuckle However, I do
feel that having to use countersunk screws to hold the part to the
fixture makes the center-to-center matching absolutely critical and
I don't think I can hold it critical enough on a drill
press...better to change the order of operations so only the last OD
trim is done on the fixture [with continuous stress in one direction
rather than the stop-and-start, back-and-forth fixturing stresses of
the graphics milling operations]... toolpost with a spindle scribe a
mounting while the other If this the radius best if, you hold one
side the cross |
| Lathe
Vibration? |
| I have a 9" which is equipped with v-belt drive from
the motor and v-belt drive to the spindle (shipped from SB equipped
this way). The belt used on the motor is a fairly new Firestone and
the belt used to the spindle is the old-fashioned 'jointed'
(overlapping strips) v-belt, which is still in great shape. I notice
when I run the lathe at normal speeds, I get vibration in the
workpiece - about .0005" worth of it. It seems to make no difference
what speed I run the lathe, the vibration is the same. I have the
motor rubber-mounted to help minimize the vibration, and the bench
is an extremely heavy sturdy, professionally built Lyon bench. I am
wondering if this is normal, or what could be causing it. If I turn,
pull, push, etc.... the spindle by hand, I can't get the dial
indicator to move more than .0001", so I am fairly certain the
headstock bearings and such are sound. I feel the vibration in the
ways, on the piece to be turned, and on the bench surface. I am
inclined to think the vibration is being transmitted through the
drive belt (the older style one). Skip
(10181) |
| Skip,
There could be a number of thing that are causing your problem. I
would try to track down where the vibration originates from. Remove
the belt from the motor and turn on the lathe and see if the
vibration is still there. If so, then there is a balance problem
with the motor or pulley. If not, replace the motor's belt and
remove the belt to the spindle. Turn on the lathe and test for
vibration. If there is a vibration, it could be a balance problem
with the "jack shaft" assembly or (more probable) the motor belt has
taken a "set" and needs to be replaced. If there still isn't any
vibration at this point (with the spindle belt removed) then the
problem is most likely with that belt (again, it may have taken a
"set"). Replace the spindle belt. I should say that I haven't used
one of these linked type belts before but their reputation is for
smoother running than "regular" belts. Webb
(10182) |
| I had a
vibration in an older Seneca Falls lathe that used the metal link
(alligator clips) to hold it together. When the belt finally ripped
I recut it and punched holes in the ends and spliced it with waxed
thread. The vibration disappeared and the belt lasted almost 10
years before it tore at the holes. The waxed thread did not break.
max (10183) |
| If your vib
is the same no matter what the spindle speed then it's in the
primary drive (motor to fly wheel) so it could be the motor, the
belt, the fly wheel, bearings in the motor, or ???
Kerry (10187) |
| Large objects
on faceplate |
| Another way it so
use soft jaws and then bore them to the contour of the part. a
little elaborate for a single part, but it offers one additional
method for holding that odd part. Dave (11873) |
| Don't forget
the classic way of doing it. Drill and tap the part and bolt it right
to the plate. Nothing turns smoother. RC
(11881) |
| Exactly what I did to machine an un-machined back-plate for one of
my new chucks. I positioned tapped holes where they wouldn't
interfere with the final piece, bolted it to the face-plate and
dialed it in. One of the best ways to make sure you have a solid
mount. Paul R. (11882) |
| Paul In the
folder with ETWs article on the cross slide milling and dividing
attachment are three articles on faceplate setups and angle plate
usage that many might find useful.
http://groups.yahoo.com/group/mlathemods/files/Lathe%20Milling/
-- JWE (11883) |
| JWE, thanks
for that link. As some of you already know, I am just learning some of
this stuff. Looks like I am going to have to make myself several
variations of angle plates for different setups on the faceplate. I
downloaded the articles that I could use.
Bill C. (11884) |
| Yes, very
nice articles, JWE. I remind all SBL members that JWE's mlathemods
yahoogroup is a "Library of Alexandria" for machinists, old and new.
Wonderful old articles on work methods that are entirely appropriate
to our vintage lathes. With much gratitude to JWE, Paul R.
(11885) |
| Paul, you are absolutely right. The articles he has uploaded are a
great source of information. If it wasn't for the various member on
these groups I wouldn't know near as much as I have learned from
everyone. It's nice to feel like part of a family that share the same
interest. JW, yourself and many others make a great effort to help
those who are just learning. You guys are to be commended for all of
your efforts. Bill C.
(11886) |
| Turning
Troubles |
| I am not very
experienced at machining and I have a problem with turning a outside
diameter with my South Bend 9" lathe. I have turned the gibs so
tight that it is not easy to turn the dials but I still get gouges
in a cylinder that I am trying to get to a specific diameter. Also,
if I power feed towards the headstock and then power feed toward the
tail stock the cutter removes material in both directions? I
generally use the rocker tool mount and I have used cutting tools
that are HSS, the "tangential tool" and carbide tipped tools. The
tangential cutting tool seems to give me the best control and
finish. I have tried moving the cross slide towards the back of the
lathe and then towards me to remove as much "play" as possible and
that seems to be the best. But what a pain to find a place to get
the tool closer to the turning center line and then move it back to
the setting I need to turn. Maybe this lathe is just worn out. I
don't use it much but I would like to be able to use it when I need
it. John
(12201) |
| John: What material are you trying to cut? Try changing the feed
and speed rate, usually the harder materials will give a cleaner cut
at slower speeds. The power feed on my 9" I only use for thread
cutting. I've found that the cleanest cuts are obtained by hand
feeding the carriage. Cutting fluid can sometimes help depending on
the material. 5000 and 6000 series aluminum likes denatured alcohol
steel cuts best with water soluble oil (milk) cast iron brass and
stainless I cut dry.
(12202) |
| John If you
are cutting in both directions it sounds to me like you are trying
to take off too much material. Especially with a rocker tool post,
it will "spring" if you are trying to slice off too much material,
and when you come back the other way, you take a bit more off as it
pushes back in. Not sure what you are trying to cut, but you may
have the wrong geometry on your tool as well. Make sure that you
have clearance, and try taking a very light cut by hand, rather than
power feed. John (12206) |
| I have a bit
of trouble following what you are doing, but if you find it
difficult to turn the feed screw, you have the gibs much too tight.
also, remove stock in one direction only - towards the headstock.
Your cross-feed screw probably has a bit of wear, or backlash. Bring
the tool a bit closer to you, then advance it toward the stock. Note
the reading when you are taking a cut. When you have finished with
one pass, bring the tool back to you, move the carriage toward the
tailstock end of the cylinder, advance the tool to your previous
setting and add however more you want to remove. That way the
backlash is not a factor. I think you were doing it backwards, which
does not remove the backlash, but makes sure it is still there! A
lantern holder is perfectly fine - you also are probably cutting at
the wrong fpm and maybe taking too big a bite. Unless the power feed
is jerky (in which case you should fix the clutch) it should give
you a smooth, even cut. Frank
(12208) |
| Frank, What you
describe is the way I have always done it. But I tried the opposite
technique to try and find a way to keep the lathe bit from "digging
into the work". I have the lathe turning on the middle pulley and
.50 inch diameter steel rod that I am turning. Also the longitudinal
feed is being run on the slowest (largest driven gear smallest drive
gear) speed possible.
(12211) |
| Is there a
possibility that your .5" rod is flexing? Not sure how long the work
piece is but this may be a problem.
(12216) |
| Have you
checked your carriage? It is flopping around any? Sumpin' is loose
unless you have a most weirdly ground bit. I don't know much about
turning steel (I usually work in brass and aluminum) try lowering
the cutting point of the bit very slightly below the center of the
work. Frank
(12217) |
| This is obviously
a medical problem.
(12221) |
| I do not
understand the comment about it being a "medical problem" Can you
elaborate? Frank
(12226) |
| Frank, I
believe the comment was directed towards the previous comment which
stated: "Is there a possibility that your .5" rod is flexing? Not
sure how long the work piece is but this may be a problem." I
believe that the length and flexibility of a mans workpiece should
be a private matter ;-) ...And now for something completely
different. It sounds like the tool profile is a little off or the
tool is sitting a bit high. I use a lot of scrap rod (mostly cold
rolled) and it is very difficult to keep from gouging. A round nosed
tool with little or no rake seems to leave the best finish. As to
the previous silliness, I use a tailstock center as much as possible
to prevent any flex in the work. Cold rolled steel is a real pain to
work with, but the price is usually right. Jeff
(12227) |
| Allen, denatured alcohol gives me an enormous
headache, but have found kerosene to give me good results cutting
aluminum. Johnny
(12238) |
| I was turning a .5 inch
diameter steel rod that was about 5 inches long. One end was in a 3
jaw chuck with the other by a "dead center" in the tail stock. The
tool might have been at the wrong height, but it was aligned by eye
with the "dead center" which had been aligned with a center in the
head stock. One of the tools I was using was a brand new indexable
carbide with a 7 degree clearance angle. Another was the "diamond
tool", which gave better results. Which case would cause the tool
bit to "dig in" more. The tool above center or below?
(12250) |
| Basically
neither is good. I would say tool below center line is the lesser of
two evils. The tool above would cause more problems of the tool
digging in. The aligning with the dead center should be correct tool
height. Smaller diameter work pieces are more critical of tool
height, but 1/2 diameter isn't too finicky. I don't know if it was
mentioned before, but check tool over hang. I think you are using a
rocker type tool holder. Keep the length of the holder as short as
possible. i.e. closer as possible from the cutting tip to the tool
post. The rocker post is a bit more flexible or less rigid than
other toolholders, still it is a good idea to keep this in mind with
other setups. With a rocker type, you are rotating the rocker up or
down to achieve center height. This affects the tool clearance
angles. If to great, you need to shim up the tool holder to keep the
tool angle/geometry correct. As too 1/2 stock, what type of steel is
being cut? Check the spindle play or clearance in the headstock. It
is adjustable. Check this in the tailstock. I don't know if you are
turning between centers or with a chuck and center. Not any real
difference though. Are you using a diamond tipped (CBN) insert or
some brand called 'Diamond'? Another thing to look at is the tool
nose radius and depth of cut. Different materials are better or
worst for finish. You depth of cut should be over twice the tool
nose radius. This keep even load on the tool. Just some thoughts.
Hard to give good advice without seeing what's going on. Tom(12251) |
| John, I have
sometimes had the work piece try to "climb" the tool when it is
mounted below center line. In effect the tool pulls the workpiece
into itself. This is more pronounced when there is a lot of overhang
as in a rocker style toolpost. The angle of the tool to the work
should be set up so that the forces tend to push the tool away from
the work, rather than pulling it in. I think there is a discussion
of this in How To Run a Lathe. Glen (12252) |
| Unless you
take very small cuts, the stock may indeed flex and you might try a
follower rest. First try taking a cut of maybe .005 and using a good
sulfated cutting oil and see what happens. also make certain you
have lubed the dead center. Frank
(12253) |
| Turning Large
Diameter Stock |
| Remember
the picture that was on this groups main page? You know, the smoke
stack one that everyone commented on? How was the piece supported at
the tail stock end? I am about to start a project where I have to
turn a large diameter (6 inch dia.) and would very much like to
knurl the piece after I turn it. My problem is, how do I support the
2-3 foot long piece at the tail stock end? I know I can grip it on
my 4 jaw chuck at the head stock end. Philip (12456) |
| Philip, a
large pipe center, witch is expensive, or weld a piece of 2x3/8 flat
across the end inside, true it up with a steady rest and center
drill it. Then you can use your tail stock and center. Cut the peace
out when you are done. Duane (12457) |
| Philip,
Use a cat head in the TS end. Other end on external jaw steps. PS,
that was not a smoke stack. RichD
(12458) |
| Rich, what is a CAT head? Philip (12459) |
| Duane, That
is such a great idea, I'm sorry I didn't think of it before!
Philip (12461) |
| Philip, I
just signed on to this group today. Glad I could help. Duane (12462) |
| I knew
you would throw the "cat" out with that one :-)) Picture a hub
(chunk of steel cylinder with a drilled center in one end) which has
3 or 4 drilled and tapped holes equally around the diameter. In
these holes are screwed in lengths of allthread or bolts with
locknuts. This can be called a spider, but sort of looks like a
starfish. The idea is to insert this carrier device into the tube
and adjust the screws outward to contact the tube wall and center
the hubs drilled center hole for minimum runout on the tube OD. At
some point you will have mounted the whole assembly on the lathe and
a rotating center in the tailstock and test/adjust for runout. It
helps if the bolt heads have been pointed to prevent wandering as
you turn them and get a better grip on the tube. Some jobs require
one cathead at each end with a center in the headstock and driver
plate/dog. Kind of fiddlely to set up, but gets a tough job done.
Turning miniature locomotive boiler ends to match up with smokebox
joints use this method. Smokeboxes are usually short enough to stay
put with just the chuck jaws. Seen in the last group pic.
RichD(12466) |
| Surface Finish
|
| I've been
machining an arbor on my 9" model B out of prehard 4041, this is for
my Burke #4 mill. Using a negative raked tool, with indexable
carbide insert, I attained a surface finish that looked beautifully
polished. Unfortunately, this was not the final cut. Thereafter, the
finish was not nearly as good. In fact it was smooth but dull, and
needed polishing to give it that proud product appearance. This is
the usual finish for me. I tried to duplicate this seldom obtained
wonderful finish with my Aloris tool holders, various inserts, high
speed steel, and by varying speeds, feeds, tightness of the work
piece between centers, etc, all to no avail. I have yet to figure
out how to get consistently superior results. BTW, I use no coolant
of any sort and prefer to cut dry. So to those for whom a superior
surface is commonplace, would you be so kind as to share your magic,
tips, and skills. Al
(12506) |
| Al: One thing
I find with Carbide tooling is that surface finish is better with
heavier cuts. Carbide does not like small finishing cuts ( .005 to
.010 on diameter ) but performs better with heavier cuts. Alas are
small machines cannot sometimes take the heavier cuts with Carbide
and sometimes are inexperience does not allow us to take a .050 cut
for finishing and still keep size tolerances. Ron
(12507) |
| Al, I have
found that a freshly sharpened bit that has also been run across a
sharpening stone always gives me a nice shine. Therefore, I rough
cut with one bit, and fine cut with another one.
Philip (12512) |
| When it comes
to the chromolly steels you need to either polish to get your finish
or take a heavier cut as a finishing pass. And as stated above the
heavy finish pass may not be possible with your machine. Cutting dry
is only for quicky jobs your tool will last longer and run cooler if
you use a coolant or cutting oil. Kerry (12526) |
| Finishing |
| Thing is all we do
on a lathe IS cut screws, or spirals. Just a matter of how to deal
with their paths. Even cylindrical grinders do this. The question
isn't what feed necessarily, so much as finishing AND accuracy. Most
tools for finishing are of a broad-nose variety. Flat tools can
chatter on machines that are either small or loose. Notice I didn't
say old. A follower-rest may be needed for long thin work. For
bench-top or tool-room lathes, a 3/8-full radius tool is all the tool
you'll need. Unless you have a very tight machine, a flat 3/8 is not
recommended. To much chatter, IMHO. If a lathe is in good trim, you can
turn a finish on alum and have the chips resemble very fine
cotton-wool. My finishing tool is the one described above. After
rough grinding with the stage set at 5 degrees, I go to my expanding
8" belt-sander and finish it on 600 grit. Then change belts for a
leather one and charge it with 50,000 diamond paste. This puts a
mirror finish on anything. Even under a loupe it looks good. Keep
this tool in its own box. That way it won't get chipped like all the
other tools. A word on expanding belt-drum sanders. The word is
indispensable. Built for the lapidary trade, the 8" expanding drum
belt sander can do a lot of work in a shop. The sanding belts come in
20 and 100 grit intervals. They can be diamond or alum.-oxide. Changing
one takes less time then reading this sentence. A can of water
dripping through the guard and on to the wheel keeps even carbon
steel cool. A 3/4" or 1"arbor is standard. This allows you to
change-off for a diamond saw blade. Now your cutting carbide into
shapes. You can sand stone, wood, or metal. The grinders that promise
to sharpen any tool are dedicated to do just that. They cannot sand
wood or polish metal; let alone cut carbide. Build an arbor To handle
this belt sander and diamond saw. The cost should be less and you'll
do more with it. Go to tile stone floor stores and see if they have
any old diamond blades about to be thrown out. If they do, you can try
out a diamond saw on HSS or carbide. In water, a diamond saw runs
cool, almost no sparking. Imagine the file-steel you can shape without
losing the temper? Now back to finishing. For super-finishing *,I'd
use a wet silicon carbide 600 grit with an old file to back it up.
Keep it wet. At these grits, you won't take off but a few tenths, but
do check your progress. It is a good way to get a grind tolerance
with a jewelers finish. A piece of leather charged with rouge will be
as far as you can go practically. For bores, I'd make up a set of
hones out of copper tubing. A t-split near the end will give you some
spring against the bore. Use 600 grit in light mineral oil to hone
with. regards, Ron *super-finishing is discussed in a book written by
the chief engineer for the SR-71 project. I'll discuss this in more
detail when there is time. Ron
(16836) |
| I forgot to
mention little things like rigidity. Anything you do on the lathe
requires a no-flex set-up. Keeping the tool close to the holder is
important. However removing all flexing is near impossible. Knowing
how to use it can be a help. Like the 'spring cut'. If your cutting a
shaft with the tool nice and sharp, and close to mamma tool post, you
still have spring. Just re-cut without moving the crossfeed dial over
the same stock. You will see how the tool and work-piece 'relax'
against each other. As for CRS, there is a way around a bad
finish. Because it is so troublesome to finish...don't. Use a coarse
feed to put thread-like tooling marks on the work. It'll make the
part look like it was turned in some huge circa 1900's lathe. A
regular tooled finish actually draws the eye along its length. If you
were to cold blue, (as in perma blue) the finish, it will look even
better. Ron
(16879) |
| Thanks to everyone for their comments on finishing tool geometry, rigidity,
and the effect of steel type. It may be of interest that the link in
FAQ that is listed first only refers to grinding a very specialized
tool for deep boring, unless I missed a more general section.
http://groups.yahoo.com/groups/mwhints Will use the sugs made and
check the other two sites plus HTRAL. Thanks, Steve (16890) |
| Finish problem |
| I thought I had
fixed my finishing problem, not. It seems my lathe has developed a
spiral finish on any turning I do. From one end to the other, all my
turning work has developed this spiral or 'barber-pole' finish. Is it
a vibration somewhere? Any takers on this one? Ron
(18341) |
| Ron- are you using
powerfeed? try 'helping' the handwheel. i found that sometimes the
clutches aren't grabbing right. if I put a little preload on the
wheel it goes away (I am putting off tearing into the carriage).
else: worm gear, swarf ? dennis
(18342) |
| Ron, Far
be it from me to offer you advice, but I too had this
spiral/harmonic finish problem on cuts anything over half bed
length.. umm, 3ft usable bed. I found my problem was bed twist and a
very small (downward) offset of the tailstock. A mate also advises
me that being just a touch too low with tool height can cause the
same symptom (similar to, but not, chatter). A fairly simple (though
a tad dangerous) way to tell if its vibration is to grease up your
palm and every inch or so of cut along to bed, give a gentle push on
the work and observe the finish. push/pull/up/down. Garry
D (18347) |
| Even if they are both within
tolerances, their relative values may set up a resonance in that
spindle. By simply changing one of the settings (within tolerance) you
may eliminate the problem. RC (18367) |
| Turning,
Boring... Titanium |
| Has anyone
here spun titanium? If so, what speed would you suggest? What tool
bit did you use? And what did you do to polish it up with? I just
bought 2 5/16 bits with 10% cobalt and it seems to cut great. The
piece I'm turning is only 1/2 in dia. and WOW did it heat up FAST!
What lube should I use? Philip (18369) |
| I have turned and
drilled titanium on my model A. The only luck I had was using
carbide tooling. I was either using WD40 of SAE 20 as a cutting oil,
I am sure there is better stuff out there. Gary (18374) |
| Gary, Just a dab of oil made the titanium just peel away
from the stock. There was nothing to it. What a beautiful metal to
work with! Philip (18388) |
| I've turned a fair
amount of 6AL4V titanium on my 10" S.B. I've had very good luck with
cobalt tools, sharpened with a round nose, with side, front, and top
clearances of 10 degrees. That might seem contrary to common sense,
but the 6AL4V Ti I work with likes a sharp tool with lots of
clearance. I turn it dry with a very slow spindle speed (middle
pulley w/backgear-about 92 rpm) for a 2" diameter workpiece. In my
case these are interrupted cuts, the work is bolted to a fixture. I
can take .050" cuts with about .002" feed per revolution on the
South Bend, and the tool will cut well for over an hour. Be sure not
to let fine chips gather in a pile. If you've ever seen titanium
burn you'll know why. I've never had problems on the lathe, but I've
had some dust go off when grinding Ti. (18392) |
| Dialing in to
center |
One of the best
advice I ever got from the net was to use two (2) chuck wrenches.
While you are centering you can move the work much more accurately
by using one wrench on your side and one opposite side to move the
work to the center. John
(18619) |
| John, I
see we have the same equipment, well the rusty file anyway. Your
suggestion gave me an idea. If I was to take some keyway stock that
fit into the chuck key hole I could make up a couple of small
"knobs" if you will, and then use your idea to center stock. It should
be easy to do and would be a lot easier for me anyway. Tom (18623) |
| Hmm, and if a guy recessed a suitable
hole in the square drive bit, he could mount a small round "super
magnet" in there, and then the "adjusters" wouldn't fall out when he
_manually_ spun the chuck around ... (rather the opposite of my
"safety" chuck key). Alan (18646) |
| That is
an even better idea Alan g little super magnets in my shop right
now. It would be interesting if they were left in though wouldn't it. Tom (18677) |
| Turning radii |
| On a
manual lathe like my 9" Model C, what're the good ways to turn
radii, both inside and outside? I was recently making a part that
had both inside and outside radii. I use carbide tool bits/holders
(mostly because its easy... No tool grinding). I tried doing the
radius by running both x y handles by hand, trying to move the x
handle faster at the beginning in comparison to the y handle, then
ending moving the y handle faster than the x handle. I.e. I was
trying to be a CNC controller. The results are squarely in the range
of "probably good enough for something that doesn't matter". I.e.
the metal isn't there and there's sorta kinda a radius. So what's
the "right" way to do it? Thinking about it, I figure a better
approach to getting a good looking radius might be to grind an HSS
blank into the shape of the radius I want, then feed that into the
workpiece. The downside is that I don't know anything at all about
grinding toolpieces. Obviously though, I can learn. But I figured
there might be better/other ways. Any advice? Mark (one thing doing
some of my own machining has done is make me appreciate the cost of
racecar parts... :-) I spent probably four hours yesterday making
one and a half 1" spacers for a spring collar. If I were going to
try and sell them, I'd need to charge like $200 ea to break even.
(18775) |
| Mark, Have
a look at this ball turner.:
http://bedair.org/Ball/ball.html It
will be self evident how it works if you think about it g something
like it to make proper curves. Tom
(18776) |
| There are a
few good articles on spherical turning and the tools to do it with
at the group mlathemods3. JWE(18785) |
| You can grind a tool (But form tools are more subject to chatter,
depends on the size of the radius) or you can plot or calculate
several places along the final tool path. (a large scale sketch of
the shape you want on squared paper is the non-math majors way to do
that) and take it in bites, then file for a finish (watch using a
file on a lathe, catching the tip on a chuck jaw and driving the
tang into your tender parts can ruin your day). John (18798) |
| John, You can
do both of what you mentioned. The form tool is good for small
radii, with a good set up and a heavy lathe up to 1/2 inch radius,
give or take. The steps, cut and file is OK too for larger radii.
They do make a swing arm apparatus for cutting radii, both internal
and external. The same tool can do both, just set up a bit
different. I have used them and they work good. Still, they need
operator touch and small cuts, but can make accurate (or nearly)
radii. I think they sell them for the Taig or Sherline for a decent
price. Tom (18800) |
| Steel |
| I work
mostly with brass and aluminum, but occasionally need to make a
steel part. What kinds of steel do you use for easy (?) turning with
HSS bits and where do you get it in small quantities. I got some
round shaft at my scrapyard and it's really tough. Or maybe I just
don't know what I'm doing. Frank
(18813) |
| I won't comment on the second part of that, but most likely, the
material is 1018 or something worse. There are dozens of grades of
steel (probably hundreds) and they range from "damn near impossible
to cut" to "cuts like butter with a hot knife". Probably the most
common free cutting steel is 12L14. Much closer to the second
definition. It is now available from many sources, in many sizes and
lengths, including McMaster-Carr. McMaster carries it in diameters
from 1/4" to 4", and lengths from 1 foot to 6 feet. Now the caveats,
before someone jumps on me. It does not harden directly, but CAN be
case hardened. If you are having a service company do so, just let
them know what material it is. It CAN be a bit tricky to weld. Not
something I do, but we have had parts welded successfully. And yes,
it contains a small amount of lead (hence the "L" in the
designation). Probably not a good idea to eat it, as it may cause
learning disabilities. I've used it for years. Knock off the
comments from the peanut gallery. There are other steel grades that
are specially alloyed for specific qualities. There is a great
resource available at: http://www.matweb.com In particular, compare
the "Machinability" of 12L14 and 1018 or 1010. 12L14: 160% 1018: 70%
1010: 55% IOW, 12L14 is 2.3 times as easy to machine as 1018, and
almost 3 times as easy as 1010. Scott Logan (18815) |
| Scott - you've answered all my questions. And in one e-mail! Frank
(18817) |
| Frank, I went
nuts for about a month trying to cut "hard steel" when I first
started about two years ago. Since then I try to use 12L14 all I
can. I purchase my stock from the Metal Express outlet in Baltimore.
I ALWAYS stop by when I'm in the area of the place and browse thru
the 'mistake and shorts rack.' One of the last true bargains left.
You'll have to do a search (Google?) to find their webpage. You may
have a supplier close and not be aware of it. Try to go in person to
take advantage of any deals. Larry
(18826) |
| Larry. I
live in the middle of Vermont and there are no metal dealers here!
Hardly an industrial state. However, there's a place in Woburn Mass
(I think it is Admiral Metals) that has a large room full of drops
and I sometimes get near there. They will also ship small pieces if
they have them. Frank
(18829) |
| How do I
radius corners? |
| I may be having a
really thick day! I now if I chuck work I can rad the corners to the
same diameter as the work but how can I achieve a e.g.: 3/4" rad on
all four corners of a 2" ? 4" ? 1/4" plate I have a SB 9" and no
milling machine
(18877) |
| For a corner
radius on the edges: mount a 3/4 radius cutter in the headstock,
clamp the workpiece at correct height to the x-slide, position the
saddle and lock it against lengthwise travel run the piece across
the cutter using the x-slide advance. voila - radiused corners (
along the edges) w/no "milling" machine. for a radius around the
corners w/ center of the radius on one face of the part mount a 1/2'
or larger center cutting end mill in the headstock, clamp the
workpiece at correct height to the compound with the center of the
radius at the center of rotation of the compound, position the
saddle and lock it against lengthwise travel loosen the compound
clamp very slightly so that it will just barely move under hand
pressure. you may need to attach a lever/handle to the part to keep
the rotation smooth but maintain clamp firmness. this rotational
clamp is not made to serve in motion this way but can do so against
mild machining forces in a pinch. somewhat tricky to adjust but if
your clamp lubrication is good and surfaces are fairly smooth it can
be done. run the piece across the cutter by rotating the compound
around its center. this is where the long handle comes in handy for
smooth rotation of the compound against the clamp pressure. voila -
radiused corners w/no "milling" machine. "ajegan001" (18880) |
| Milling on a
lathe isn't the easiest thing to do. I have used an angle plate
bolted to the cross slide with shims under the part and the part
clamped to the angle plate. Its a cheap way to mill but not
something I would do on a regular basis. JP (18882) |
| Brilliant
idea regarding the use of the compound. It had crossed my mind but I
thought it may have been a No No in engineering terms. Tony (18897) |
| Can
someone please please explain the relationship of the X Y Z axis to
the lathe for me one more time g milling machine as well. I hate to
sound so dumb but I can't stand it any longer. I read these
wonderful ways to do some operation and get lost trying to figure
out which way is up g cutting endmill as referred to in the post
below? Tom (18900) |
| You may want
to hold off until you try it before you comment on how smart it
is... if the part is small and you don't have a mill holder with
enough stickout from the headstock you may get into interference
with travel of the saddle, wont go close enough to the headstock.
there are a whole batch of possible problems with doing things like
this on the lathe. we would normally try to make sure the machining
forces on the compound are always in the down direction where
possible but they may be made more controllable with the long
handle. just a few more ways to separate the feline from its
integument but it can exercise your ingenuity a good bit to overcome
the little bumps. "ajegan001" (18902) |
| First of all, I believe the "x-slide" referenced in the earlier post
meant "cross slide", not "X Axis". Having said that, it is helpful
if everyone used the proper terminology in referring to the various
axes. "Z" Axis always refers to the axis of the spindle. On a
vertical mill, that would be the vertical axis. On a Lathe, it's the
axis along the spindle to the tailstock. If the machine has only one
other work axis (such as a standard lathe), it is referred to as the
"X" Axis. If the machine has a total of three axes, such as a
Bridgeport or similar mill, the longer of the two "non-spindle" axes
is the "X" Axis, and the final is the "Y" Axis. There are three
other commonly used axes, but not common on manual machines. "U"
Axis refers to rotation around the "X" Axis, such as a horizontal
indexer on a vertical mill. "V" Axis refers to rotation around the
"Y" Axis. "W" Axis refers to rotation around the "Z" Axis. Scott Logan (18903) |
| Tom, For CNC
machine controllers: on a lathe - X = cross feed (cross slide) Z =
long axis feed-lathe bed (carriage) Y - not used or aux axis on a V
mill- X = long axis feed, table (left/right) Y = short axis feed,
table (in/out) Z = vertical feed, spindle, cutting tool holder.
Rich (18905) |
| Rich I
had it all mixed up like I thought. Tom (18907) |
| Heavy 10
vibration |
| When I am using the collets set up the lathe will cut
perfect and no vibration. Now when I switch it over to the chuck the
hole cabinet and lathe will vibrate so bad it chatters the work. I
have cleaned the threads on the chuck with no success. I have yet to
bolt the cabinet to the floor I wanted to ask if this was necessary?
when I first bought the lathe I did not have this problem but I
moved the lathe since. It is level but I used steel plates to do the
job as my floor was not level. Tom C. (19259) |
| Interesting
challenge. I'd look at the mounting bolts that attach the chuck to
the faceplate. Have you examined the status of your head stock
bearings? I have a heavy 10 and have not experienced this
difficulty. I definitely would not run the lathe until you fix the
problem. Is the thrust bearing on the left end of the head stock
spindle snug? Lubrication OK? I know the above ideas are not rocket
science but it is all I can think of at the moment. I am in Burke,
VA. If you are near by I'd be glad to drop over and have a look.
Eric (19260) |
| Sounds to me
that your chuck is either out of balance or out of round for what
ever reason. Have you replaced or removed the jaws in the chuck for
some reason? You say that the lathe has been moved, nobody dropped
the chuck did they? For your lathe to work flawlessly with the
collets not with the chuck, it seems to me the problem should be in
the chuck. Good luck and let me know what you find. Chris (19261) |
| Easy enough
to check if the chuck is at fault - put another one on (borrow if
need be). Unlikely that the vibration is cabinet - esp if you've
leveled and shimmed. The lather should not vibrate and it is a sign
of unbalance somewhere - systematically track it down - sumpin's
gotten loose. Frank
(19262) |
| Sounds to me
like you jaws are not in correct order. Look on the end of the jaw
for the number, then check the face of the chuck to make sure the
number matches. If you get #2 and #3 jaws interchanged it would do
exactly what you are describing. Paul (19263) |
| Thank you
for the quick responses. I will try all your ideas and thank you
again. Tom. (19264) |
| May be
your problem lies on tool angle. Try with front angle about 6§ Capipio (19266) |
| If it is not
the chuck out of balance then try to isolate the problem. The steel
plates should be flat and have no air spaces so they don't act like
springs. The floor should be rigid, a wooden floor can be a problem.
Remove the plates and see if it still vibrates. Also look carefully
to see if there are any cracks in the cabinet legs. JP (19282) |
| I was
thinking about it and if isn't the chuck, check the back of the
spindle to see if there is a lot of slop. I've never seen it but it
could cause a vibration with the chuck but not the collet. Paul
(19283) |
| Remove the
jaws from the check and run the chuck and test for vibration.
(19284) |
| Tom, Does the
lathe vibrate when the chuck is turning but you are not cutting? or
does the vibration begin when you start cutting? I have a friend
that had a similar experience and found the chuck was cracked around
the ways that the jaws slide on. The vibration only started after he
began cutting. Mike (19285) |
| Thank you for
all the responses. This is what I found. When I tighten down the cap
screws closet to the chuck it will chatter and vibrate, But when I
loosen them no chatter at all. When I try to lift on the chuck when
it is stopped It will lift up a little. So I messed with expander
screws the same thing happened if I would tighten them down and
chatter would happen loosen them and it would go away. I know it is
not rocket science but I am lost when it comes to these expander
plugs and screws. I did check out the chuck No cracks but when I did
separate the back plate from the chuck there was some sort of putty
looking stuff. I scraped it out and cleaned every thing up nice. I
think the problem is somewhere in the spindle. Tom
C (19308) |
| Tom, Sounds
like you need to adjust the headstock bearings first. The expander
screws and cap bolts need to be tight. Then do a pull test. First
loosen the tension on the flat belt, then place an indicator as
close to the bearing as reasonable on the spindle outside of the
headstock. Place a pipe into the spindle and at a 1 foot distance
press down with about 75 lbs of pressure and note the indicator
reading, then pull up with 75 lbs of force and note the reading
again. The reading should be less than .002" between the two
measurements. Do the same on the rear bearing. This procedure and
the procedure to adjust the bearings is in the parts manual CE3458.
It may be in the files section here also, I am not sure. JP (19312) |
| Large dia.
turning on a 9" |
| You can turn the
outside dia of any disk that will clear the carriage. Mount a tool
on the dovetail that is normally used for boring, of an Aloris of
Phase II QD Tool Post. Turn the post 180 Deg. so it is on your side
of the post. Tighten the QD tool holder and unscrew the tightening
handle (so the handle does not run into the chuck) Note: make sure
to tighten the tool bit good because the forces are pushing the bit
out of the holder and not into the holder as normally. Gary
(19483) |
| Gary That's a good
test of the quality of your QC Toolpost. Actually you can use the
same style of trick to turn the OD of anything that will clear the
bed. Personally I wouldn't dream of trying this sort of thing with a
tool in a QC holder, not even a first quality Dickinson, let alone
the the imports that are all us normal HSM types can afford. This
type of job tends to be a quick route to chatter city and, on a
small lathe you need all the help you can get. With even the best QC
posts the extra slides and restricted clamping areas work against
you. The biggest boring bar you've got in a heavy block or 4 way
post is a more reliable approach but what you really need is a
Gibraltar post, basically a hefty block which fits in the hole
normally used to carry the top slide. Loosing the top slide cuts out
several fixed and sliding joints so everything is more rigid and
provides plenty of room for a really hefty tool. I've got a 1 1/4
inch boring bar waiting for met to get round to turning a lump of 5"
square steel into a Gibraltar for my Heavy 10. That baby is gonna be
solid and will have plenty of mass which always helps tame any
tendency to chatter. Probably only get used every other year but when
I need it nothing else will do. I've never understood the the
enthusiasm for QC posts unless you can afford enough carriers for a
comprehensive selection of ready to use tooling. Block or 4 way
posts are easy enough to make and, with the SouthBend T-nut fitting,
pretty much as quick to swap if you make a full unit complete with
nut, stud and handle. Tool height setting is easier too if you make
up an off lathe gauge. I tend to run off a brace or three when I
fancy an easy job. 8 so far, all 4 ways, with another 4 specials to
go. Clive
(19498) |
| I agree, Gary, I've
used this trick with my Phase II toolpost to turn chuck backing
plates for my 8" Junior. I had to keep the cuts light to avoid
slipping the drive belt, but the setup was rigid enough to whittle
down cast iron or mild steel. My next project will be a 7" backing
plate. (19548) |
| Spinning
aluminum |
| I was wondering
which type of aluminum I should turn. I just want to see how
differently my bits will react and see if I can learn something from
it. This is just for fun, but I was wondering if some one could
suggest a type to learn on. I have access to 6061, but I'm sure
someone has a suggestion. Philip (20968) |
| Philip, 6061 is the
best choice. Actually, round extruded stock typically will be the
only or most found material at metal sellers. I work at a Tech
College where the materials provided for the students is 6061 and
12L14 steel. My scrap box is slap full of their boo-boos. RichD
(20969) |
| Philip, I just
noticed the subject line again. Do you want to do spinning or
turning? For spinning 1100 or 3003 al sheet. For turning 6061 bar
stock. RichD (20970) |
| Rich, I will be
turning, sorry, my mistake. Philip (20971) |
| Howdy, 6061 has
been fine when I've used it, but I think 2024 and 7075 machine a bit
better overall. I think any of those three will do what you want. I
_wouldn't_ use the AL you can get at Lowes or whatever... 3003
maybe? Whatever it is, its very, very soft and the finishes I've
gotten have stunk. Mark (20973) |
| Rich Is there a
source where one can buy 12L14 steel in smallish amounts? Bar as
well as plate. I'm on the east coast and the specialists who sell
small amounts of metal all seem to be west coasters and the freight
charges are killers. Frank (20978) |
| Frank, we buy a lot
of stuff from Metal Supermarket. There's a store near here. They
don't have everything and I'll bet it depends on which store you
call. I like digging in their dumpster! They seem high, but the
alternative means buying full bars or sheets and truck shipping
expenses. See for a store location:
http://www.metalsupermarkets.com/ RichD (20979) |
| Turning a
concave radius |
| How
would you turn a concave radius on a lathe? I know on a wood lathe
you just grind your tool to the shape you want. What I want to make
are a series of dies for a compact bender to bend tube. The concave
radius will support tube sizes from .5" to 2.5". (21035) |
| Andrew, the top
slide (compound) swivels. Set the tool tip in relation to the slide
center and set the locking screws to allow rotation without
looseness. The only gotcha will be the slide hitting the chuck jaws.
Most radius turners require lots of stock overhang anyway. RichD
(21043) |
| You can cut
aluminum with a tool ground to shape. I made a 1.75 inch die this
way. But, I think a radius cutter would be better but have not tried
it because dies for tubing 1.5 inch and larger need to be 12 to 14
inches in diameter which means you need to have a large lathe. Check
www.pro-tools.com for the
radius of their dies. Andrew Booker wrote: How would you turn a
concave radius on a lathe? I know on a wood lathe you just grind
your tool to the shape you want. What I want to make are a series of
dies for a compact bender to bend tube. The concave radius will
support tube sizes from .5" to 2.5" (21058) |
| Turning a
CONVEX radius |
| Turning a convex
shape is something that comes up from time to time however I have
really never read a good responce. So often I wish I had a method of
cutting a convex shape. I have seen the picture someone has posted
to this group, but I do not own a miller so there is no way I can
make one on my own... If anyone knows of a method to make one or
maybe finds one on Ebay, please keep me in mind. Philip (21064) |
| It depends on the
size of the lathe. Usually about 3/8 to 1/2 diameter is about max on
a mid size lathe. This also depends on material. That is using a
form cutting tool. Softer material, then the bigger the radius you
can cut. I have used the radius cutting tools. They work very well
and are accurate. They do make them for the Sherline lathes. They
might be a bit small for our SBs, but I think you could adapt them.
Worth a look and I think they are about $60. For an ID, you could
make a pivot with a tool bit at the end. If you make the length
adjustable, then you could set up for varius radii. Tom(21077) |
| I have a 16 inch
SBL, so I don't think I'm limited to such small radius. (21083) |
| It depends on
how large of a radius you need to turn. I don't actually have any
experience with the Sherline one. I would think you would need to
make a block of some sort to space it up. What you might try, and
this is very Jerry rigging, is to use the compound rest. Set up a
lantern type tool post, and offset the tip of the tool bit from the
pivot point of the compound rest. Might be worth a try. Still it
would depend on the radius you are cutting (large = better) and the
profile of the part. With a 16 inch SB, I would say you might get up
to 3/4 radius with a form tool, in mild steel. Kinda on your own as
far as setup. I do a lot of setup on the fly, so its hard to give
exact info on how I'd do it. Tom (21084) |
| Turning any radius
greater than the size of the tool is doable on any lathe. Convex or
concave. thing is even with a radius cutter, you have to remove bulk
material before you finish with the radius. Think back to math
class- equation of a circle is x^2+y^2=r^2. Ellipses same thing. Set
up a simple spreadsheet to figure out the step increments to rough
out the work. It should look like stair steps up and down. 50 thoug
over (x), is a good increment to start with. Figure out the plunge
(y) for a given radius. Then I would use a form tool or radius tool
to clean it up. use a template to guide you. For the task at hand,
the dies and even the follower block for the tubing bender, they
don't have to be perfect. I would rough them out on the lathe (or
better yet a mill) and the to make the finish use a full size form
tool. on my bender, for onsie-twosei bends, I make up die blanks of
laminated 3/4 plywood and use a router to make the whole thing,
grooves and radius and all. I have used plastic as well for dies,
makes for really easy working and they are very durable too. dennis
(21086) |
| Machined
finish expectations |
| A question was
posed to the Southbend and 7x10 groups this morning as to what one
can expect in a turned finish with carbide or ground cutting tools.
The normal finish to be expected from cutting tools on a lathe or
mill is called 120 and is to the eye and touch rather coarse and
rough. The best one can expect from a lathe or mill in careful
turning with very sharp tooling is a 63, good finish but not what
the person posing the question wants. Now to get a finer finish than
a 63 micro one needs to go to other methods than cutting tools and
proceed to grinding and and/or lapping. Now grinding with
lubrication and a hard fine wheel can get with care and light cuts
down to an 8 micro finish, but still not the mirror finish the
person posing the question wants. A mirror finish is called and
shown on the micro finish comparator as a 2 micro finish and can
only be obtained by turning on the lathe or mill to about .003 to
.005 thousandths of an inch over the desired finish size. You would
then grind with a coarse wheel or lap with say 180 wet/dry paper and
oil to .001 oversize. The next steps would be straight lapping with
first 220 grit, then 440 grit and finally 600 grit to .0002
oversize. The final step would be with polishing rouge or a good
automotive car polish to desired finish size and desired mirror
finish at 2 micro finish. Archiving a mirror finish and a dead on
size slip fit part is doable but requires intensive work to produce
extremely tight fits and high brightness finishes. Also these
extreme high finishes are not very good for rotating shafts where
lubrication of bushings or bearings is needed. High micro finished
parts used in rotating or reciprocating will usually gall and fail
rapidly because there are no low places to retain lubricants so wear
is rapid and failure certain. JWE (21078) |
| Maximum depth
of cut turning mild steel |
| I have a 1957 10K.
While reducing the diameter of a 1" mild steel bar, I have been
practicing with different tool shapes, angles, rates of feed,
spindle speed, etc., in trying to determine the maximum attainable
depth of cut. Cutters are tool steel, sharpened and honed. The
deepest cut I have managed so far is .012 in. What is the deepest
cut that I can expect to achieve? What is the deepest cut that you
have achieved? How did you do it? (21646) |
| Warren, There are
quite a few variables involved, rpm and longitudinal feed being only
two, but one question I have is how long is the 1" dia bar and is it
supported at the tailstock end? By the way, you should be able to
take off considerably more than that ... at least .060" per pass.
What is happening that is preventing you from going deeper? Part
deflection, surface finish, tool breakdown, machine stalling ? Mario
(21651) |
| Mario, on your 10K
you should be able to go .250 on a ruff cut. Duane (21652) |
| Duane, I know that;
I just didn't want to overwhelm Warren. As I said, there are lot's
of variables involved, and I'd really like to understand just what
kinds of problems he's running into so we can better help him out.
Mario (21653) |
| Warren, I have not
done much turning on my 10K but when I bore CR steel I can easily
take .200 inch on a pass for a hole increase of .400. I use the
lowest pulley speed and the lowest feed. I do this boring daily for
the parts i sell on eBay. I use HSS bits that I sharpen. Bob (21660) |
| I'm tinkering on my
1967 Heavy 10 and bent a 5/16 carbide cutter 20 degrees taking a
3/16 cut into a 1" mild steel rod @ 55 RPM. The feed was somewhat
too fast, I cant remember exactly, but it was moving at about can
opener speed. The steel was peeling off like orange rind. I managed
about 1" of cut when the bit failed. Later my machinist friend told
me that is very hard on the lathe and the tooling. It makes me
think, lathes are capable of great capacity, but is it prudent to
run at max? What are you going to save other than 4 minutes !! And
what could you lose? If cost of tooling is no object then go for it.
If lathe parts can be found cheaply and repaired easily, go for it.
My machinist says he roughs at .010 and finishes at .005 on both
feed and depth of cut at top running speed 1450. When I watch a
finish turn off at these rates I can see the wisdom behind the
process. It only takes a little more time and repetition to achieve
a desired diameter reduction, with the least wear on lathe and
tooling. And the finish is generally ready for final dressing by
filing and emery. (21667) |
| The bar is 8" long,
tailstock supported. The belt slips and the bar comes to a stop. I
am using the slowest spindle speed without using the back gears. I
haven't measured the speed, but it appears to be about 200 RPM. The
belt is flat, and appears to be made out of a canvas type material.
The belt and pulleys are oily (are they supposed to be?). I tighten
the belt to deflect 1" with a firm thumb like the book says. Warren
(21668) |
| Sounds like you
need to replace your belt. Also, the slowest speed isn't always the
best. Speed or RPM is dependent on diameter of part and the
material. Softer part faster speed. Smaller diameter faster speed
(RPM). There is a formula for this. The material surface speeds are
given by a table. I forget the formula off hand. I think mild steel
runs about 80-100, while aluminum is about 200. So you'd run
aluminum twice as fast as mild (1018 etc.) steel. Depth of cut
really depends on the HP of the machine. .050 should be on problem
for a 10K. 0.100 it should handle also. Some mentioned .2-.25, I can
believe that, if a good setup. .010 in another post sounds very slow
and a waste of time. Still, its very dependent on your lathe and the
part to be cut. There is a reason for different size of lathes.
Large parts need large lathes. Small parts are best run on small
lathes. Now I am sure someone will rip me and say 'Yeah I run small
parts on large lathes or vice versa. I can too, but it a lot easier
and faster to use the proper size lathe if available. Now for
finishing depth of cut. The feed should be less than the tool nose
radius. The depth of cut should be at least twice the tool nose
radius (TNR). The feed so the TNR doesn't skip over material, ie
thread. The depth of cut, so the TNR is stabilized in the cut. If it
is only cutting on the radius, then the tool bounces. So, fix the
drive belt system, calculate speeds and feeds and go from there. If
you need help, let me know the steel (mild 1018) and the diameter of
part to be turned. 1/2, 1 inch etc. Tom (21669) |
| The belt and
pulleys should NOT be oily at all. The belt should be leather or
leather faced, not canvas. This is definitely one of your problems.
You can look up cutting speeds in the machinery handbook or htral.
It is listed in ft/min for different materials and tools and is a
good starting point. JP (21670) |
| I have a synthetic
belt on my C with a "canvas-like" inside face, that is excellent.
Theoretically, leather is more likely to stretch than some of the
synthetic types. Leather is of far poorer quality than it was when
most of these lathes were designed for leather belts. Also, leather
for belting was cured in a different way, and cut from the hide in a
particular position (against the backbone) and in such a way that it
was less prone to stretching. Animals go to slaughter far younger
nowadays, with the resultant hides being far more "baby skinned"
than they used to be. Apart from a "faithful" restoration, I'd plump
for a good synthetic every time. Len Smith, many years as a harness
maker Maximum depth of cut when turning mild steel The belt and
pulleys should NOT be oily at all. The belt should be leather or
leather faced, not canvas. This is definitely one of your problems.
You can look up cutting speeds in the machinery handbook or htral.
It is listed in ft/min for different materials and tools and is a
good starting point. JP (21671) |
| Warren, You may
have found your problem. The belt should not be oily. The first
thing I would do is clean the belt and pulleys with a solvent to
remove any oil or grease, and try it again. I suspect it will be a
lot better, but if it still slips, you might try spraying a littler
belt dressing on the pulleys and belt. It wouldn't hurt to clean up
the pulley faces with some light abrasive paper no courser that
220 grit! Let us know how you make out. Mario (21672) |
| Len, That's a very
interesting point you make about "younger" leather...very
interesting. I also have one of the synthetic belts (rough inner
fabric, shiny black outer surface) on my 10K. I have also used a
modern automotive "serpentine" or micro-groove belts as a
replacement and they work fine. I wondered which side to use against
the pulley. The grooved surface, which is softer, and designed to
be the 'drive' surface, or the back side, which has more surface
area. Actually, it seems to work just as well either way...of course
I don't usually rough-off .250" a pass!?!? Mario (21673) |
| Wow, one-hundred
thousandths (an inward movement of .050" on the compound) in a
single pass on a SB 10". Seems like a lot and would put considerable
stress on the entire system. What's the rush. Eric (21674) |
| When the alligator
link broke on my belt, for a couple of weeks I used what had been an
2'.6" diameter, round section, O ring from around the door area of a
washing machine. It was about a half inch thick. It pulled it into
place with some stretch in it, and superglued the joint. It worked
fine, and I cut it off and kept in case of a similar emergency. Len
(21675) |
| I have taken 0.050
with hand feed speed set by feel. But you had better be sure your
have everything well secured at that depth. I use 0.020 or 0.030
most of the time with a power horz feed set to give the finish I
want. Had 1 inch dia in 3 jar parting with 1/8 wide parting tool.
Tool Caught and pulled the part out of chuck and bent the parting
tool. Not something I want to repeat on my 10K.. nothing else hurt
.I had about 3/16 grip on the end of the 1 inch dia round, Would
have liked to use my collet setup , but it only goes to 5/8 dia.
Darrell (21681) |
| I'd say that your
running WAY to slow. With HSS bits, you'd want to run at 300-400
RPMS (CS*4/D (90*4/1 gives you 360 RPMS)). The cutting speeds for
carbide are two to three times faster than those for HSS. Whether
the lathe can handle/will let you run at the RPM is often anther
story. For example, my bench mill has a 1/3 hp motor on it, and it
cannot run a 1/2" end mill in steel at 720 RPMS, because of the
limited torque of the motor. The I would say your bit failed because
you were running to slow. CNC programs use very fast roughing feed
rates (in IPMs (inch per minute) rather than IPRs (Inch per
revoltion) because they have steppers or servos on the leadscrew
rather than a gear train from the spindle) Running to slow kills
carbides faster than anything because the friction coefficient is
greater with Carbide than sharp HSS bits. Carbide doesn't get the
edge that HSS gets. Later my You run at the speed closest to the
calculated (CS*4/d). On a 4" diameter workpiece (mild steel) you
certainly would not want to turn it at 1450 RPMS. Turn that at the
speed closest to 90 RPMs, when using HSS. All cutting operations,
except shapers and planers, you use cs*4/d to calculate the RPMS,
because if you ran your 1" HSS Silver and Deming drill bit at 3,000
RPMs, you would burn out a drill bit every hole you drilled. What
are you going to save other Using the example above, you would not
want re-sharpen your drill bit after you drilled a hole. At some
point the time time spent reseting/resharpening your bits takes the
fun out of machining. The RPM formula puts in the ballpark where you
have to be, so that whenever you want to cut a part, you are
balancing machining time, tool edge life and optimal cutting speed.
Finishing cuts have faster cutting speeds than roughing ones. While
the machinist you know is running over by a bit, he's found that it
works. I don't strictly follow the formula, and I turn 1" CRS bar at
600 RPMS using HSS on my 9x20, and the lathe doesn't complain. When
you get more experience, you'll know what works for you, and you
won't even need the formula anymore. I judge cutting speed by seeing
what color the chips are coming off, how the lathe is taking the
usage, and overall how smoothly the chips are coming off, then I
increase or decrease my speed from there, using the "calculated RPM"
as the starting RPM, for workpiece diameters I don't handle often.
Since I turn 1" and 1.5" often, I don't look at the RPM chart and
just chose the belt position that I've found works best for those
diameters. Gabe (21689) |
| This is where the
Machinery's Handbook rears its head. Buy it and use it. The
information contained is vast. Unless you are working with some
exotic material that has been only widely available in recent years
a 50 year old edition will work just as well as a new one. It will
give you two optimal feed rates. One is for maximum production for
given tool wear (which is what a commercial shop will use) and the
other is for maximum tool life. Most of the members of this list
will be using the latter. If you are operating your equipment at
less than the optimal tool life rate you aren't saving anything
unless your equipment is damaged. And with many metals less than
optimal rates actually increase the force required! Gene (21694) |
| It is great to have
people to talk to with real experience. Not everything is in the
book. Based on what you all said yesterday, I got up early (before
work) and cleaned off the belts and pulleys a bit to see what I
could see. Upon clean-up, the belt appears to be either some kind of
composite, or material backed leather (it looks pretty old). The
belts and pulleys were very greasy and oily and will get a thorough
cleaning at my next opportunity. Then I'll see if I can get a heaver
cut than before. By the way, I'm not dismissing the machinists
advice of .010 rough cuts at high speed. I like the idea of going
easy on the tooling and lathe; and will probably adopt that
procedure. Who wants to stop what they are working on to fix a
lathe? Not me. Warren (21697) |
| The grooved side
has MORE surface area to drive the driven surface. That's why they
do this design. Not only does it provide MORE grip due to a
"wedging" effect in the driven pulley grooves, if you were to
"stretch out" the VVVVV surface you would see it is MUCH wider than
the width of the actual belt. Look at this for a "simple" example...
______ VVVVVV. Peter (21698) |
| That doesn't seem
too much to me. I have a 1949 vintage (Australian) Herbert Lathe (I
guess it would be equivalent to a 7x24). When I want to remove a
"substantial" amount of material e.g. 1" down to .5" (on mild steel) I
would take around 1/16th" (0.0625) per pass to get close to the
required size. Using a TCT lathe tool (without coolant!) at the top
speed of approx 600-700 rpm, this is NOT a problem and does not
stress the lathe. I soon know when the cut is too heavy when the
belt slips :D There's no rush - but when a substantial quantity of
material is to be removed, WHY would I want to make 6 passes at
.010, or (as per above example) 24 passes instead of *4*! Sure, the
lathe being used has to be able to withstand what you intend to do
with it. Some lathes cannot sustain such cuts and that's ok.
Peter (21700) |
| 3/16 is pretty
deep. How To Run A Lathe, Southbend 1942, pg. 36, says 5/32 "when
the lathe spindle speed is correct and the cutting tools are
properly ground and set." This is based on a feed of .005 inch per
revolution. Cutting speed of 60 surface feet per minute which is
about 200 r.p.m. for a 1 inch rod. Speeds and feeds and the formula
are explained on page 50 of HTRAL for both roughing cuts and
finishing cuts. (21704) |
| Peter, You're
absolutely right. When mated with a grooved pulley. I was talking
about using it on place of a leather belt on a flat pulley. Sorry if
I didn't make myself clear. Mario (21707) |
| I've been wondering
about that too. Your machine may handle 0.25 in a pass but why? Is
this a new sporting event; extreme lathing? (21745) |
| Turning
Titanium |
| Problems? Methods?
Cutting tools? Threading? I've never messed with it before. Dave
(21939) |
| Sharp carbide
inserts, high speed. Titanium doesn't cut the same on each pass,
sometimes less and sometimes more so approach the finish dimension
slowly. Ceramic insert tools are common in a production environment.
Its also expensive stuff to make mistakes with. Its strong like
stainless and light like aluminum and has a high heat resistance.
This metal IS FLAMMABLE so use caution and keep a class D
extinguisher handy. At the very least a shovel and pile of clay to
smother it while you shovel the burning chips outside to where it
can burn out. JP (21940) |
| This does not
involve machining operations, but may be worth mentioning: Back in
the late 1960's I bought a set of Wiss right and left hand tin snips
(the kind with the red and green handle covers) from a nearby
industrial supply house. The salesman told me that the ones they
stocked were specially hardened for cutting titanium. The blades are
marked "S1" as I remember. He said they stocked them for a customer
who got much longer life out of them than the regular snips, which
were dulled after only a day's cutting. Steve (21956) |
| Steve, The piece of
stock I have is 3/4 thick and about 5" square. Not sure snips would
be of much use. From the answers I'm getting here, I think I'll just
hang on to it as a conversation piece, or sell it on ebay. There is
really nothing I know of that I want to make with it. Anybody want
to buy it? dave (21974) |
| Do you know what
kind of titanium it is? Grade 2 Ti cuts a lot like a softish
aluminum. Grade 5 is a bit more difficult, and tends to "stick" to
tools. Aggressive cutting is recommended to avoid dulling tools.
Try using the grinder on it, the sparks are pretty cool :) (a
waste of titanium but still fun). james (21977) |
| Turning
barstock |
| Finally scraped up
the incentive to try out the heavy 10 since I got it home and
cleaned up. I got a handful of cutting tools in the deal but most
are pretty chipped up. A couple look okay, so I chucked up a fairly
short piece of round stock in the three jaw and faced it. The bit is
centered pretty decently, as there was no nipple when done. Anyway,
I decided to try a little turning to get some experience before
cutting something important. Seems no matter whether I cut left or
right, 1 thou or five, I can't seem to get a smooth finish. Not a
finish cut, but just something relatively the same all the way
across. There are grooves scattered all through the work. I am hand-
feeding as I have not figured out how to feed slowly and not use the
thread cutting gears. Do I just have some really crappy cutters or
maybe the angle isn't right? Or maybe I am getting chips under the
bit. Brian (22287) |
| Maybe all three. To
get a smooth finish you need a HSS bit that is honed and polished
and power feed. Don't let anyone bs you in stating that they can
feed by hand smoother than the power feed. Step 1 would be to bolt
the lathe to the floor and level it. Get the book How to Run a Lathe
from Lindsay for $7. Instructions as well as most of the info you
will ever need in running a lathe is in there. That will become your
bible. Tool angles, relief, etc. Also look through the files section
for info. Don't waste your time with the brazed carbide tipped bits
they are less than useless. If you need to use carbide use the
replaceable insert type. Get HSS 5% or 10% cobalt and sharpen a few
up per the bible and stone the edges to polished finish. These
should cover most all of the cutting you will ever need. On the 10L
the power feed is not the half nuts used for threading. The half nut
lever is on the right, the power feed direction lever is the middle
one and the gizmo on the left is the power feed clutch. Some models
use a lever and others use a hand screw. The small print on the QCGB
plate is the cut per revolution with the power feed. JP (22289) |
| Brian, I am
relatively new, but have found the South Bend "How to Run a Lathe"
book indespensible for these types of quick questions. The tool bit
grind diagrams in there are just what you need to get started. Lots
of other information. Copies are available at several on line tool
merchants. I have not figured out how to feed slowly and not use the
BR. Mike (22290) |
| JP/Mike, First
thing I bought was a copy of the Southbend book. That's what got me
to thinking I had problems with the cutters. Being somewhat green I
am still working out what all of the levers do. The book no matter
how much info it contains does not say,"...to turn at X speed and
feeding from right to left do this in this order:..... " I was also
thinking I need to turn the piece at a relatively high speed but
feed slowly. I am for sure headed for insert holders. So much harder
to screw up with. The sharpening deal will have to wait until Santa
brings me the grinding wheel? Brian (22292) |
| Carbide insert
tools are expensive, nice for cutting stainless or titanium. HSS
bits are $2 to $5 and you can get a bench grinder for $50. Drop a
broad hint to Ms Clause. Anyhow the book does say turn at X speed,
read it my friend, surface ft per minute for a specific material.
Diameter of the stock and the rpm is calculated. If you are real
lazy then just use the middle belt position for small mild steel.
Remember the 'little numbers' I mentioned in the last post? Try a
few around .001 to .01 and see the differences. JP (22294) |
| Brian Listen to JP.
I started out with inserts and they certainly aren't fool proof.
It's easy to get HSS sharper than carbide so it is easier to get a
nice cut. Carbide doesn't work well for taking off 0.001" at a time
as it seems to need more pressure to cut. You end up increasing the
pressure and then all of a sudden it takes a big cut and you have to
start all over. Carbide is also brittle and you will sometimes snap
off the tip. This is especially so when doing interrupted cuts.
Grinding HSS isn't that hard to do. I'm not sure the angles are as
critical as some would say. As long as you have some rake and
clearance it will work. Maybe not good enough for a production
environment but it works for me. Your grinding will only get better
with time. As long as you don't have much overhang you don't need
1/2" or even 3/8" HSS. I use a lot of 1/4" and even some 1/8" bits.
Someday I'll get around to making tool that will use 1/8" as
inserts. I just hate grinding away most of a 1/2" bit just to get a
tool that only needs to be 1/16" wide. If you don't have a bench
grinder, a dremel works fine for grinding the smaller bits. I've
also seen some pictures of belt grinders being used to sharpen
tools. I still have some carbide inserts and I do use them for
hogging cuts but usually switch to HSS for finishing. I've only been
doing this for a couple of years so it may be worth less than $0.02.
John (22297) |
| For Speed/feed
info, start with your machinist's handbook. It has all the info. If
you need to buy one, try eBay. I got a 1959 for $11. it has all the
info I need. It will walk you through the computation of feet per
second and feed rates. Each material is unique. You may also try the
local library for a basic machinist text book. If your local Junior
College has a tech dept. try their book store. I can make
suggestions. Ping me off list. ,"...to turn at X speed BR. Mike
(22298) |
| I took a close look
at the tool I was using this morning. It has an added brazed insert
of some sort. It is ground about 60 degrees for either finish or
threading. I got this lathe from an ex-motorcycle shop, so I'm
assuming they were threading with it. I got the power feed engaged
at 224 tpi, which is the slowest thread feed. The spindle is still
turning at a pretty good clip. However, it now looks like I am
threading at an extremely fine pitch. I thought one of you said that
I could disengage the threading portion of the gearbox and just
power feed at a slow rate. I mist have missed something. JP, you are
right, the book does give you the speeds, etc., but I am still
working out how to get the back gear in/out, etc., and you can see
from the above that I forgot how to power feed a bud's 10K. It has
been a few years. I agree about the tools. The bench grinder is on
the list. I have a big dog belt sander, but that puppy hid under the
bed when I dragged that brazed carbide insert across it! Ah. Just
figured out that I have to pull out the sliding gear to drop the
feed speed by multiples. Brian (22299) |
| Mike, I figured out
that I was not pulling out the sliding gear, which was keeping my
feed rate up pretty high. I do have the SB handbook and a parts
list, but it would be nice for us greenies if there was somewhere
that it said to make such and such a cut, pull out the sliding gear,
set the gearbox at X, set the forward/reverse lever in the proper
position, check the belt location, run your tool up to the work and
set the center and distance, and turn on the lathe and start the
feed. I know that is really anal, but for us guys that have not been
doing this forever it would be helpful. I also realize that in no
time, all of this will become old hat. A friend of mine suggested I
take a machining class at the local community college, but I have
made several phone calls and emails to the teacher in charge of the
class so I could talk over the curriculum, but have never received a
reply. Brian (22300) |
| The brazed tools
are brittle pieces of junk. The carbide inserts are expensive but
you can get different grades of carbide. Carbide requires higher
speeds and more tool pressure and never really give a smooth finish,
relatively speaking. Someone may blast me on this but... You can
shape a HSS tool on your belt sander or the 4" angle grinder. Finish
the surface by hand on an India stone and then for a polished finish
an Arkansas stone. Polishing the tool by hand isn't required except
for a finish cut. The roughness of your tool will transfer to the
work. 5 degrees relief is a good starting point. Read the damn book,
THINK a bit about what you read and try it out. Don't worry about
making mistakes, that's part of the learning process. Just keep body
parts out of the way, I assume circumcision in a SB lathe might hurt
even with a sharp HSS bit. JP (22305) |
| JP, I scavenged
several pieces of material just to practice with, steel rod,
aluminum, brass and Teflon. Wanted to learn on scrap, not the real
thing. Brian (22306) |
| Brian, Have you
ever had Chinese soup? The noodle appears to be about 27000 feet
long, I think they have a contest to see who can make the longest
noodle in china. One single noodle for the entire pot of soup! When
you turn a piece of steel or aluminum, set the speed and feed to
make one continuous chip, a one piece steel wool pad. Don't use your
fingers to move it use a piece of scrap or a paint stick. It can
give you a nasty, dirty cut, metal shards and oil and dirt. (22309) |
| Brian Its not
really a good idea to use scavenged material for ab-intio practice
sessions. No telling what the stuff is. Most relatively modern
manufactured things use fairly special materials or surface
treatments. Usual problem is that a material optimized to machine
well with heavy cuts and carbide tools at about a zillion rpm when
submerged in coolant won't behave well at the sort of speeds and
feeds we use. You will usually (some stuff is just impossible) be
able to handle it when you have cracked the code but not right now.
Some of the drawn to size or specially rolled stuff is disgusting to
work with having horrid internal grain structure. Naturally Mr.
Soads law says that the really nice bit of just the right size
salvage is almost impossible stuff, just easy enough to convince you
that you are getting somewhere but guaranteed to tax even the most
expert in search of a good finish. Once you have figured out the
basics invest in some good quality free cutting leaded steel and
practice. Good material will let you get a decent finish relatively
easily and allow you to play about with tool angles and sharpness to
see what happens. Only difference with more difficult materials is
that you have less tooling and operating tolerance to play with.
Hang on to a good bit of practice steel to go back to on those
occasions when you need a confidence boost and a reminder that you
can get a good finish. (22320) |
| Sounds like you had
bad experiences with brazed tools. I use them allot myself but you
do have to invest in a set up to grind them and pay attention to C2
C5 depending on material to cut. Harbor Freight has a nice Baldor
style offhand face grinder that I can highly recommend if you want
to have the ability to properly sharpen and or touch up brazed and
insert tooling. The Silicon Carbide wheels it comes with though are
very hard and I found it best to replace them with softer wheels.
Another thing to be aware of is never shock carbide with water,
grind slow and allow to cool. I do place the steel shank in water
with brazed tools while grinding taking care not to touch the
carbide itself. From the sounds of it you are getting the cracks in
the carbide from shocking it.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46727
This grinder has been on sale frequently in the past, I caught mine
for $99 though lately it seems to go on sale for around $120. Since
the 6" face wheels are an industry standard you can mount an alum
oxide wheel for HSS on one end as well. Various diamond and boron
wheels are also available but can be very pricy. I agree with HSS
being the best for finish especially when the work is thin or
impossible to rigidly mount. Also when our RPM limits can't reach
the SFPM carbide requires. You definitely want to stick with
positive geometry tools with smaller equipment the negative rake
tooling requires heavy duty equipment to use. You also would do well
to check out the different HSS types and properties. M2 is easy to
sharpen but M42 T15 hold an edge much better in abrasive and high
heat situations. You know right away when you go to sharpen
something other then M2 its allot tougher to grind. Mark (22322) |
| On-center tool
use |
| I, as a novice, was
shown how to put the point of your toolbit at center height of your
work by capturing a steel rule between toolbit and work. I know this
is a well known trick but how many experienced guys still use this
method? How many of the novice use it? How often? Is this an
accepted, accurate method for the general home shop project? Tim
(23872) |
| Tim, I have been
guessing for 25 years. The only time I get to critical is when I am
facing a part I want flat. Most of my toolholders are designed to be
on center with a certain bit and I can't change them much. Bob
(23873) |
| Tim, I started with
a Unimat in 1963. Now have multiple lathes, mills, and manufacture
machined goods. If I don't use a fixed height gage to set/check the
tool, I use the face to a pip method. Start out low, face cut to the
center, then adjust the height until each cut shows the tiniest pip.
That's best. If the cut wipes out the pip, too high. Of course,
sharp tool edges are required. The rule trick may work, but hard
steel against a carbide or nice HSS edge is not too keen. RichD
(23874) |
| I have used this
method in the past. It works OK. Just use a flat piece of steel
about 1/16 thick. A Fishtail or thread gauge works well. Put it
between the work piece and the tool bit (while on the lathe). Turn
in the dial to put some pressure, but not enough to break the tool
bit. If the flat stock tilts to the back of the lathe on the top
side adjust the tool down. If towards the operator then up. I
usually use the center in the tailstock to adjust tools, if I use a
QC tool post. Still, I'm use to the Swiss style and it has 360
degree rotation. A center in the headstock will work too. Some tail
stocks will have a center line scribed into the quill. They also
make a gadget to set the tool on center with the OD of the work
piece. It has a level bubble. The bad news is that besides the
centers on the headstock or tailstock, setting a boring bar isn't
fun or doable. Maybe with the centerline on the tailstock, if your
lathe has one. Tom (23875) |
| I used that "trick
of the trade" when I am setting-up my cutters. Especially when I was
using a lantern style tool post. Now that I have a QC tool post, I
need to use that method very infrequently. The ruler I used is not
that hard so it doesn't damage the cutting edge of the tool bit.
When I am real fussy, I will set a square across the ways with the
blade sticking up to use as a reference for the ruler to visually
gauge against (eyeball comparison test). It is a good trick to know.
Webb (23876) |
| I have heard this
idea, but haven't used it yet. My first thought is that it sounds
pretty easy, and would well enough if everything else was pretty
square - meaning the workpiece is centered of chucked very well
right off the bat. My second thought is that if someone was first
chucking or putting the new workpiece on centers, the workpiece may
not be well "on center" itself, hence giving a false reading......to
the degree of inaccuracy of the non-surfaced workpiece. Also, this
would be exaggerated by small diameter work pieces. I would say
making a jig that sits on your bed ways and is always set on center
height would be a better long term answer. Bernie (23877) |
| There were plans
for a jig in the August 2004 Machinists Workshop magazine.
Essentially it was a piece of threaded rod mounted on a small piece
of flat stock that sat in on your ways. Then there was a nut that
you could adjust up and down to set the center height. You then
simply lined up your cutter to the nut and off you went. Mark
(23878) |
| In my hobby shop I
chuck a dead center I made into my chuck/collet and align my bit to
the tip before I chuck my stock. I know this will not work in all
cases (like having to change cutters during machining) but it does
give me a "true" piece to set my next cutter up by. This technique
can get you with in .001 to .003 of center with practice. I have
also in the past used the cutter to make a fine "scribe" line in the
stock (granted I use a lot HSS the scribe line is placed where I
have to do my next machining) to give me a reference for my next
cutter. Chris (23879) |
| It is the only
method I use. It is as accurate as any other method available to the
home machinist. (23880) |
| Turning 4130
Chrome Moly |
| My son is entering
the 2006 Darpa race http://www.darpa.mil and was asking me if I
can turn 4130 chrome moly. I'm assuming I can (9" Model A SB), but
was wondering what it involved. Does it turn like 316 stainless, or
is it more difficult; does it require carbide bits, etc? Dave
(24238) |
| Dave, I turn 4130
and it does turn harder. I have used carbide and HSS bits. The only
real problem I have had is facing to a shoulder and trying to keep
it flat, It seems to run out a few thou. But I will keep trying. I
find it at work in the dumpster G my tool post is 4130 and I turned
the bottom off with no problem. Bob (24241) |
| So you think
turning (for example) a 3" diameter shaft down to say 1.33" might be
a son of a gun? Sounds to me it will be, but I wanted to talk to you
guys first. He's wanting some machine work done (I don't have the
specifics of what he's got in mind yet), but a machine shop quoted
him $1800 for four of these things made, including some splines,
shoulders and accurate holes. I'm not to the point that I can do
splines yet (nor the correct tooling), but he was trying to reduce
this cost if I could turn it down. Dave (24242) |
| Dave, Have him drop
half of that ($) and pick up a used Bridgeport to make the splines,
etc. Both of you will benefit. Pay particular attention to the stock
you get, some of it comes annealed and some does not. JP (24243) |
| YOU CAN BUY THE
EQUIPMENT YOU NEED WITH A QUARTER OR LESS THAN THAT!!! So I think
you should, instead of giving it to someone else to buy himself more
equipment. Bernie (24244) |
| Dave that might
be a big job on a 9". I just took a job in turning 6 pcs of 3" CR
down to 1". I had to stock up on my carbide inserts. I will let
everyone know how it going in a few days. Bob (24251) |
| Any bigger job than
this hunk of RC-40 pre heat treated 4130 I am making a milling head
spindle out of. The setup shown is to face off and center drill the
bar for the BB center. The spindle was then turned down to a slip
fit for Timkin bearings. I have not finished it yet because of
moving to a new house and increased hours at work. The quill shown
next to the spindle was also machined from 304SS on the SB 9" and
fitted to the housing as a light slip fit. Oh yes the 7075T6 head
housing was also totally machined and bored on the lathe. JWE
(24255) |
| Turning 430
Stainless |
| Anyone have any
tips on turning 430 Stainless? It's 2" OD and I'm facing, drilling a
1" hole, turning a step and then cutting off. I've tried a standard
square cut C6 Carbide tool at a fairly slow speed and it isn't doing
well. How bad does this stuff work harden? I haven't tried to drill
or cut off yet. Both of these scare me after my current experiences.
I plan on playing with speeds, both chuck and feed, and trying a
little heavier cut, but thought I'd throw it out for advice. Dave
(24427) |
| Dave, Work hardened
stuff can get super hard, I had a soft to start stainless piece that
rounded file teeth. To avoid work hardening, use sharp tools, don't
drag a cut or stop in the middle of a cut. If you start a cut, light
or heavy it doesn't matter that much just make sure you finish it. A
dull tool will certainly harden your work on you. Very sharp HSS
might give better results than carbide. Jim (24428) |
| I cut stainless
almost daily at work on a 1890's lathe. I used VR/Wesson tnmg VR75
carbide inserts at a spindle speed prob half as mild steel. Don't
know exact spindle speed. I had to take fairly light cuts but I also
had to go over 4 holes in certain spots of the part. Those inserts
worked the best of any I tried. Bob (24440) |
| Dave, I agree with
using carbide tooling but would add that you should use coolant
liberally! I have drilled, turned, and milled SS with coolant with
good success. When I have tried machining dry, I always get work
hardening. George(24455) |
| In the home shop
with a small lathe very sharp and well lubricated HSS will probably
be easiest to handle. Best to have a small tip radius for strength
but it must be well polished and carefully blended in to the
straight sides of the tool. You need to cut deeper than the tip
radius, probably by at least 10 thou and the leading edge of the
tool needs to meet the surface being cut at less than a right angle.
Something like 80ø ought to be OK. Stainless materials tend to be a
bit pernickety about cutting speeds, frequently rather high speeds
are needed for best results. Biggest problem with the work hardening
variety is that you cannot take a finishing cut with the usual large
radius tool run at low speed. You have to get the finish off a
significant cut. Small lathes frequently have problems with rigidity
and power preventing you working under optimum conditions.
Realistically a 9" SB can't be expected to shift more than about 1
cubic inch per minute of tough material per spindle horse power (up
to about 2 or 3 for aluminum alloys and the like). The hefty plain
bearing spindles of Heavy Tens and the bigger machines make life
much easier as you can do some serious leaning on the tool without
things bouncing around. Last bit of stainless I did on the H10
peeled down nicely at about 1/8 cut and fairly high speed but you
could hear it work hardening momentarily during the process and
close examination of the swarf showed where hard bits had been dug
off. That particular stuff was very difficult to hacksaw and peeled
the teeth of a bandsaw blade in nothing flat. Clive (24459) |
| Thanks to everyone
who answered. Sounds like playtime finding the best speed and tool.
The Carbide I have is brazed and it's unknown what grade. I used a
new bit but didn't hone it. I don't have a coolant system on the
lathe but with a cake pan and a large pump lubricant can and I can
simulate fairly well. My dad did it this way using Kerosene. I'm
surprised we didn't burn the shop down. Sharp tool, uninterrupted
cuts, play with speed and keep it cool. Got it! (24479) |
| How to set
angles |
| The way I was
trained uses a set of log/trig functions, a sine bar, joe blocks,
and a dial indicator. Refer to the sine tables for the angle you
need. These show up in Machinery's Handbook. Stone the side of the
compound for burrs. Then figure a way to lay the sine bar and Joe
(gage) blocks against the compound. The compound is set rough with a
piece of good round stock in the chuck. This means you dial the
whole rig until you can adjust the sine bar parallel and touching
the bar. Then for the final, use the dial indicator in the chuck and
move the apron/saddle back and forth until it is zero. Keep in mind
what you are doing is only as good as the condition of the ways,
gibs, nut and screw assy. To use an edge finder. Place a piece of
stock in the vise, and tighten it. Put the E/F in the quill and
tighten. Turn on moderate speed. The E/F will run wobbly. As you
crank in the dial, it will slowly stop running out of round. Look at
the dial, making a mental note. Now carefully crank the wheel until
you see the E/F go out of round. Look at the dial again. Bring back
the dial beyond the point it went out and come to within .001/.002
of the mark. Depending on how it looks, either move in a bit more or
stop. Most E/F's have a .200 tip. By moving the dial .1 past the
wobble-point is exact center. Nut'n to it. I have seen rank amateurs
make fools of themselves before...or at least until tonight I
thought I had. Tom has done a grand thing. Though a bit winded, he
has set the reputation of the bar back beyond Hammer hobby. Ron
(24612) |
| Ron, I agree with
you completely, I have a 6 inch sine bar and gauge blocks and would
use these for real precision. I jumped into this one when the
original querist wanted to slew his top-slide and take a 1 thou
finishing cut and was told to set it over to 84.261 degrees, but not
how! Perhaps I should stick to iron and drop the irony. Now on my
9SB the top slide degree graduations are about 30 thou apart so it
shouldn't be too hard to set it by eye to say the nearest 1/4
degree. Now sine of 5-3/4 (5.75) degrees is 0.1002 which is pretty
near bang on for the purpose required which was a fine finishing
cut. Now let's suppose inaccuracies in the machine and the setting
lead to a small error and the top-slide gets set between 5-1/2 to 6
degrees. For 5-1/2 degrees sine = 0.096 which is 4 hundredths of a
thou short of what our friend wants and for 6 degrees sine = 0.105,
5 hundredths of a thou over. The chap didn't ask for toolroom
precision and I know how I would set up that final facing cut.
Frank (24628) |
| Frank I do not even
try and use the built in protractor for anything. At $29 from Enco
almost all the time the machinists protractor with the magnifier
built in. It makes setting any angle a simple matter with guaranteed
accuracy. If not this one then one of the $9.99 ones also does the
job better than the built in one that you can not see from the front
of the machine without a mirror. JWE (24632) |
| Further to Ron's
excellent description of how to set the top slide angle accurately
using a sine bar there are some other equally effective methods for
those who don't, yet, possess a sine bar. As ever with angles it
helps if trigonometry does not induce a state of abject terror and
brain malfunction. Running a DTI against a faceplate or test bar
over a decent feed distance, inch ish, is effective. I find it best
to measure the feed needed to achieve a given DTI deflection, you
may prefer to work the other way about with a fixed feed. Sine bars
work by having a fixed length lever and variable gauge block stack.
Going the other way works just as well. A drill set provides a nice
selection of close tolerance spacers and its relatively easy to
calculate how far along a lever you need to be to set small angles.
Its quite tolerant of length errors too. For example 1/16 at a foot
is a few hundredths short of 0.3 of a degree, at 11 1/2 inches its a
few hundredths over. For many practical purposes you can do well
enough with a pointer and a ruler, if you are familiar with them,
radians are a lot easier than degrees when working in this manner.
Home made vernier scales can be effective. Usual problem is getting
things big enough so that the scale is open enough to read easily.
Oversize verniers spanning more than one calibrated division will
work well but I find them a headache to read. Moving the slide round
by small a mounts is difficult, push and tap gets there but can take
along time. If you possibly can fake up some sort of "twin push
screw on a bar arrangement" to give positive movement in both
directions. Owners of lathes fitted with a long, T slotted, cross
slide will find this much easier. On a related topic angular off-set
of the top slide is often touted as a way of getting very fine cuts.
Although this is geometrically true the actual performance depends
on how good the cutting tool geometry is. For all practical purposes
the actual cutting edge "radius" between the top and front surfaces
of the tool needs to be less than a quarter of the in feed depth to
get a clean cut. So if you are trying to take half a thou off the
cutting edge radius needs to be better than about half a tenth which
is pretty darn sharp. Although the tip radius, i.e. as viewed from
the top, itself will be much, much larger the finish and blending
needs to be of similar standard. Being such a fine cut there is no
way the tool can be re-sharpened, you have to go with what you have
got after the previous cut(s). Its easy to forget that the tool
travels a long way during a job. For example during a 6 inch cut on
a 6 inch diameter bar at 5 thou per rev feed the tool tip travels
over a quarter of a mile! No wonder it looses its edge. This is why
a few heavy roughing cuts and light finish cut is a much better
strategy that creeping up with loads of fine cuts. If the tool edge
is insufficiently sharp it will rub rather than cut. Metal will
still be taken off but it all gets a bit unpredictable. Clive
(24652) |
| Attaching
outboard spider |
| I couldn't find
anything in the archives on the subject of attaching a spider to the
spindle. This is for a 10k. I'm thinking maybe use a set screw,
however the spindle is somewhat thin and would be worried about
distortion, damage etc. The other possibility I can see is a
threaded collet type. More complicated to make less possible
problems. Anyone been there--done that on this type lathe and have
any experience? Dan |
| Dan: On my 13" I
had about 1" of thread left showing where the Locknut for spindle
thrust take-up was so I made a threaded piece that went over spindle
and threaded on there. It overhung past the spindle and that is
where I put in the grub screws to use it as an outboard spider.
Can't say if your 10K is the same arrangement or not. Ron |
| On a 11x36 Logan I
used to have the previous owner had made a new spindle thrust take
up nut which was used instead of the factory take up nut. It had the
spider built right in, very simple , and it worked fine. Dee |
| Dan writes: I
couldn't find anything in the archives on the subject of attaching a
spider to the spindle. This is for a 10k. Tell me what you're
talking about. I could make some wild guesses but I'd rather get it
right from the start. Anthony |
| Anthony, I believe
we are talking about a spider which is actually a cylinder with four
bolts/screws to hold a shaft centered in the outboard end of the
spindle. Gunsmiths use them to hold the action end of the barrel
when working on the muzzle end at the chuck. Did I just confuse you
more? Dee |
| Please excuse my 'newby-ness'
but what is an outboard spider, what is it used for and how do you
use it? Tom |
| I am referring to a
centering device that fits on the back side of the spindle, there is
a photo of one on the cover of the current issue of Machinist's
Workshop. It's used to hold long work pieces such as rifle barrels
fed through the headstock. Dan |
| Sounds very similar
to what I have always known as a cathead. Basically a tube with four
setscrews coming into the center to hold irregular shaped shafts and
provide a bearing surface for a steady rest. You could go one
further in this idea and machine one end to precisely fit the
outboard end of the spindle. Roy |
| The left end of my
Heavy 10 has a tube with 4 screws in it for centering/supporting
long shafts through the headstock. My tube goes over the existing
end of the headstock tube. Also on the collet tube my dad put 4
screws in it for holding barrels during gunsmithing operations. He
used brass screws to minimize any scratching etc. Enjoy. :-) Eric
Basically a shaped shafts further in the spindle. |
| Dee writes: I
believe we are talking about a spider which is actually a cylinder
with four bolts/screws to hold a shaft centered in the outboard end
of the spindle. ---- Did I just confuse you more? Sounds like a
spindle-tail pot chuck. Used to assure axial alignment. Do I win the
prize? Anthony |
| Helical
pattern in part |
| I was hoping
someone could give me some advice with my 1967 10" South Bend. There
is a helical pattern left in the part when I make a finish cut. I
cut mostly plastic with the lathe, but it does the same thing on
aluminum. At first I thought it might be the lead screw, but it also
leaves the pattern when I make a manual cut. The only other thing I
can think of is that the chuck is out of balance, which it seems to
be since the machine does have some slight movement when it is
running. Maybe someone has had a similar issue? I would appreciate
any input. (25837) |
| I just went thru
this with my 10K. It left the most perfect helical pattern. Mine was
a leveling problem. Once I got the headstock way end to match the
tailstock way it end prob went away. Bob (25839) |
