| Knurling Do's and Don'ts?
(Jul 20, 2001) |
Knurling question (Apr
18, 2004) |
| Knurling tool for lantern
(Jan 24, 2003) |
Phase 2 knurling tool
(Apr 18, 2004) |
| Knurling (Mar 31, 2003) |
Decent Knurling Tool (Dec
9, 2004) |
| Knurling (Apr 6, 2004) |
|
| |
| Knurling Do's and Don'ts? |
| Anyone have
suggestions on how to go about knurling? I have a piece prepared
that I'd like to apply about two inches (lengthwise) of medium
knurling to. Is the knurling applied using manual control or under
feed? Should several passes be taken to get to the correct depth of
the knurl pattern? If several passes are taken, how does one assure
that the tool stays in the pattern? Should low speed be used? Jim (1139) |
| I would practice on a test part
first. If the pitch of the knurl isn't a multiple of the
circumference of the part, it might not come out too good. Change
part diameter if needed. I take one pass, slow rpm, lots of black
cutting oil, under power feed. You can reverse the feed and go back
if a little more is needed, but I wouldn't take it out of the
pattern and restart. Push the knurling tool (or wrench it down, if
you have the clamp type), and rotate the part back and forth by
hand, as more pressure is applied, until you are a little shy of
the depth you want. This seems to help get it started properly,
especially if the pitch is off a bit. Don't go too deep, or it gets
messy looking, nowhere for displaced metal to go. Leave a small
flat on top. It takes a little practice, but you'll get a justified
sense of accomplishment when it comes out crisp. (1140) |
| Looks like
excellent advice. I'll give it a try on a test piece. As a rule of
thumb, do you use a power feed in the middle of the range?
Jim (1141) |
| OK, so I'll stick my foot in some
good 'ol shop manure. An operation of this type really puts your
creme-puff on PMS. Punishing MY SouthBend! I'd do this with some
sort of 'clam-shell' type of rig. On hand-screw machines we use a
tool attached to the top or side of the lathe. It can also be bought
along with a quick-change tooling system. Hmmm...I'm not really
doing this justice here, so let me start again. Knarling is in my
humble opinion THE WORST THING YOU CAN DO WITH YOUR LATHE! Your
taking a PRESSING tool and jamming it against those 'not so young'
castings and bearings. In the words of an MSC instruction sheet, "In
order to get a real good imprint you must (GULP!) jam the tool
against the work". Call me a sissy if you want but I'd rather eat
babbitt bearings before I'd do this to my lathe. Instead get this
hear unit that works like a clamp and exerts it's own pressure while
putt'in wrinkles on your work. When that lathe was young, you
probably could do this on a lathe. But it really will put a strain
on everything involved. If you must, buy an old junker with a
worn-out everything and rig IT to do yer dirty-work! Ron
(1142) |
| I'd agree
completely with Ron, and I would not use either the single or dual
knurl pivoting head types on my Heavy 10 for the reasons he stated
unless the material was soft and an aggressive (deep) knurl wasn't
necessary. Fortunately, there are two other types resembling Ron's
clamshell approach that are fairly benign. The first is probably the
best you can get, and that is a fork shaped arrangement which has
two knurls opposed on the ends of the fork. See
http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItemitem=1617693953 for an example of this Cadillac of the knurling
world, though this particular one is a big 'un. (It's not mine - it
just illustrates what they look like.) This is the type of tool used
for the cleanest knurls in a production environment, using a fine
wire brush to keep the knurls clean and plenty of lubricant as the
knurls are feeding. With the B S style, you can do both straight and
diamond knurls with the same straight knurls - the guides rotate to
whatever angle is needed. The other style is the scissors type that
does about the same thing, but in my experience has rigidity
problems with tougher materials unless you get a robust model. Your
experience may differ, and that's fine...either type places only a
reactive torque on the spindle and tailstock, which they were
designed to absorb. Properly set up, they don't put any pressure on
the bearings at all, which is ideal. The drawback? More time and
"fiddle factor" to set up, and the B S style does require 2 or 3
tools to cover a complete range of diameters. The side feeders are
pretty much set and go, at the expense of bearing wear and a level
of breathtaking apprehension way above my tolerance level. The
high-end Brown Sharp knurling tools come up on the bay place all the
time - I think I paid all of $40 for mine, and it runs from .375" to
about 1.375" with a convenient 1" shank that fits the Aloris boring
tool holder perfectly. Do a Google search on rec.crafts.metalworking
using 'Bastow' as the author and 'knurling question' as the subject,
and you'll see a good description of its use, along with what a real
machining master thought of them. They *do* work beautifully, even
on stainless steel! Mike (1144) |
| Evening everyone,
I'm joining this discussion a bit late because I've been gone for a
few days. First of all, I would like to say that I am partial to any
type of straddle knurl holder. This type greatly reduces the
destructive force applied to the machine components. I used to have
a #5 Gisholt turret lathe and one of the regular jobs I used it for
was putting about 8" of 20 TPI diamond knurl on 1-1/4" 304 stainless
tube which was fabbed into grab handles used on fire apparatus. This
was an interesting learning experience. I used a straddle knurling
holder which was shop made by someone. I bought it used for next to
nothing and modified it to use standard knurls, shoulder bolts for
pins, homemade bronze bushings so the whole thing was renewable. The
first thing in using a tool like this is to set it so that you get a
full enough knurl by cross feeding in to about .015" short of
center. This ensures that the tool will not pass over center (you
won't like it when that happens). Then the long. feed could be
engaged using around .020 IPR. This would make a nice clean knurl in
one pass. One problem I did find was not being able to change the
blank diameter since the tubing was already finished. I got around
this by grinding a small amount off the O.D. of the knurls to make
them track properly. Worked every time. Tom
(1160) |
| You can get them
from Enco. Larry (1230) |
| Knurling tool
for lantern |
| I need to find a
knurling tool to use with a lantern style tool post on my 9A. I've
heard the clamp type is really the way to go, but everything I've
seen is set up for a quick-change tool post or four way tool post.
I've looked in Enco, KBC, Mcmaster, etc. and the shanks all look too
wide to fit in the lantern. Tom (8883) |
| That shouldn't be a
problem - most used machinery dealers have scads of these and they
are available from Victor in NYC
www.victornet.com Frank (8885) |
| KBC list some.
Import and USA and Armstrong. They list the Clamp type too. Shank is
1/2X5/8 or 5/8X3/4 ($114 or $155 for USA or $60-80 import). The
regular type Cost $15 for the pivot head or $40-55 for the
multi-type. I thought I saw them in MSC. KBC's number is
1-800-322-4292. Tom (8887) |
| I
checked out www.victornet.com , but didn't see what I think will work. I
guess I should have called it a scissors type. The ones I've seen
all have a shank at least 1/2" in width, more than my lantern post
can handle. Maybe I'm being overly paranoid about needing a scissors
type? I've heard the other style puts too much pressure on the bed
ways. Tom (8888) |
| Tom, I have an
older MSC catalog. It list The clamp type or adjustable with a 3/8
shank. 1/8-1 capacity. It cost $123.20. Order # 08656027. Tom
(8889) |
| Tom, Another
solution would be the hand knurlers. They don't mount to the tool
post. MSC list two : 08681330 for $116 or $221 with 6 knurl set and
08681371 for $251. It looks like a pipe cutter. Tom (8890) |
| Mill the shank to
fit. Make a new lantern post large enough to fit an unmilled
shank. Rick K. (8891) |
| Victor has a 3/8
width shank self-centering knurl (not a scissor) in their paper
catalogue for $24 bucks or so (I am looking at a yr old version) I
bought one and it works just fine with my lantern holder on my 10K.
Call them up (1-800-723-5359) and tell them its on page 48 of their
2001/2 catalogue. they also show a scissor type, but it seems to me
that the shank is horizontal - not vertical. Personally, unless you
are going into production knurling, I don't see that the forces will
damage your ways. Use lots of oil, a very slow spindle speed and
feed the tool in slowly. It will take several lateral passes to get
the depth you want. I knurl a lot of brass knobs and just take my
time with it. Frank (8892) |
| Tom, For my 9" SB I
purchased the Enco (imported) Scissor type knurling tool on sale for
$30 or $40. I removed the 1/2" x 5/8" arm and the pivot bolt
throwing both away. I made a 1 1/4" x 1 3/4" x 2 1/4" high alum.
block, drilled a 5/16" clearance hole vertically (with the 2 1/4"
dim.) for a mounting bolt threaded into a CRS 1/4" thick plate sized
to fit the T-slot in the compound. I then drilled a 3/8" horizontal
hole 1 1/ '32" up from the base (SB distance from top of compound to
centerline, check your machine). Put in a longer 3/8" pivot bolt
through the two scissor arms and thru the aluminum block and your in
business. Works great and is much more rigid than the original
arrangement. CRS in lieu of the aluminum mounting block may even be
better, I used aluminum because it was available and quick and
dirty. Makes for an inexpensive, very usable, rigid, knurling tool.
Neil (8893) |
| Knurling |
| I have seen many
comments both here and on other boards about the negative effects of
using a non pinch type knurling tool. The consensus seems to be that
the lateral force required is hard on the bearings of my 9". Unless
I miss something would not using a steady rest with the knurling
tool on the tailstock side of the steady rest relieve the lateral
forces on the headstock by being taken up by the steady rest?
Perhaps I over estimate the support available from the steady rest.
Does anyone know the answer to the viability of this technique? Jim
(10043) |
| Jim, The pinch type
is a superior method of knurling. Much easier to control and
independent of the lathe cross feed. My worry with the old style is
use with regular chucks getting the jaws sprung plus the stock to be
knurled does not get overstressed. My usual parts are short stubs,
so a steady rest would be no help. Building a pinch (scissors)
knurler is an interesting project to make one. There are several
plans floating around. I have built my own. RichD (10044) |
| Knurling is not
just hard on the spindle, its hard on the apron too. Think about how
the force is applied to the work with a single sided knurling tool.
these lathes are not that rigid. the only resistance to horizontal
loads is the incline of the way. Forces against the incline have 2
components, 1 horiz, the other vert. I will try to describe but w/o
pictures, it may be hard to follow. Horizontal force will make the
apron climb up the way until the bottom plate catches which resolves
the vertical force. then the two work together to resist the force
of the knurling. Pick up the apron on the machine. How much play is
in there? that's enough to drive you batty. for single sided knurls,
draw a picture of the knurl wheels and your work. Draw a radial line
at the point of contact of each wheel and the work. Center to center
of the knurl wheel to center of your work piece. Now draw the 'components'
of those radial lines: these can be described as sin and cos of the
angle. The two vertical forces are equal and opposite and cancel.
the horizontal force is the sum of the two horizontal component. Now
apply that horizontal force to the v way. to get and equal horiz
component of the reaction on the 70 degree v to cancel the force of
knurling, you have a relatively HUGE vertical force. That will go
unchecked until the apron bears on the bottom of the apron. Scissor
knurls by design will resolve the forces internally. one up, one
down, the only one left is the resistance to travel along the work
which is trivial. If anyone wants, I will sketch and post. dennis
(10048) |
| Didn't SB
themselves offer a QC toolpost with its OWN built in knurl? This
thread has worried me a bit, having an older lathe that already has
some slackness through wear. Seems like the scissors knurl would be
worth posting in the files. Len (10050) |
| Since we're on
Knurling, I have another type of knurling question: so far I've only
used the diamond pattern knurls with two rotating wheel cutters. I
want to make some simple straight-across (parallel lines, parallel
to the long axis of the work) and see that there are two types for
sale. One is a single wheel, the other is a more conventional double
wheel (same as used for the cross-hatch or diamond pattern) How can
one get a neat, clean, simple knurl if there are two wheels? since
there's no way to align or synchronize each wheel, won't it bugger
the knurl? Has anyone any tips about the single-wheel knurl? I knurl
brass only - should I worry about the lateral loads on the bearings
as per the previous few postings? Frank (10051) |
| Not to argue about
the knurling but south bend shows and lantern style post with a
knurling bar. Now for one lantern tool posts stink. And when you're
trying to push the tool as hard as can into the piece of steel it's
no wonder it moves. knurling can be done in a south bend lathe with
a standard knurl it's just not good for a machine that has seen some
wear ( and when was the last time you fired up you brand spanking
new lathe?) It was probably fine back in the day when some one else
owned the machine and you just ran it but this is your machine and
if you break it you have to fix it. Kerry
(10054) |
| The best
general purpose knurling tool I have ever used is a hand-held three
knurl device. Essentially the thing is a pair of handles about a
foot long pivoted at one end, like a nutcracker. One handle carries
two matched knurls about 1" apart and the other a single knurl which
lies midway between the opposing pair when the handles are parallel.
The pivot point is a bar with a series of holes to adjust the
spacing of the handles so that they are more or less parallel when
the tool is squeezed onto the workpiece. A stop screw sets the full
squeeze travel. Having set the pivot point position to suit the
workpiece diameter the tool is simply squeezed onto the workpiece
with the lathe running is a slowish back gear speed and held until
the desired depth of knurl is obtained. For longer knurls a slight
sideways pressure in the desired direction causes the tool to move
up and down the workpiece. Plenty of lubrication and a bit of
patience gives a good knurl remarkably rapidly. With good sharp
knurls it works well on all normal materials although really tough
steels can a bit too much for it. Surprisingly, considering the
normal load applied to conventional knurls, you don't have to
squeeze terribly hard. Firm handshake (not knuckle-crusher) is about
right. Too hard is as bad as too light. Basically you have to get a
feel for it. The main disadvantage is the difficulty in putting a
knurl in a precisely defined place. Usually one can trim to size
afterwards but if it really matters I have been known to do the
knurl first and make the rest of the part around it. Besides putting
virtually zero stress on the lathe this tool seems to be immune from
the annoying double knurl effect obtained when conventional tools "mis-register".
Scissor type twin knurl tools can be exasperatingly sensitive to
set-up it this respect. ( I have read magazine articles going into
great detail as to how to calculate the exact starting diameter to
get perfect knurls. If followed the procedures are said to "usually
give perfect results". Unfortunately the various sets of
calculations give different starting points so I suspect there is an
element of workshop joss involved.) Personally I suspect that many
problems encountered by HSM types are due to old, blunt, knurls and
attempts to force the pace. Clive (10059) |
| Accu-trak (
http://www.accu-trak.com/metriccuttype.html )
has some pertinent information on that very good question about
tracking of multiple knurls, Frank. In the General knurling section,
it says, "Two methods of specifying the comparative tooth spacing
are currently in use - CIRCULAR PITCH and DIAMETRAL PITCH. snip
Unlike gearing, only four standard pitches are used (64, 96, 128,
160) for blank diameters from 3/32" to 1". Diametral Pitch dies are
designed to permit accurate tracking on standard fractional sized
blanks, making blank diameter selection easier." Having said that,
they also add in the Knurling "Tips" section, "Since proper tracking
is usually established after only one complete revolution of the
part, the "secret" to success is to RAM THE DIE INTO THE BLANK!! By
forming a deeper, wider impression on the first revolution, the die
teeth are more likely to "step" back into the initial grooves the
second time around." So...there is obviously a bit of slop
associated with the forming process to allow the "stepping" to occur
on each revolution. I have both forming and cutting knurl types for
my HLV-H, but I have all but abandoned the B S forming knurl tool.
It's useful for increasing the diameter of worn shafts and the like,
but in work-hardening materials like stainless and brass the peaks
can appear 'crumbly' and uneven under a microscope after finishing,
depending on the material, tool angles, pressure, and forming depth.
The cutting knurl tool doesn't take any more power than normal
turning or facing, has a capacity for 1/4" to 6" stock, and does a
much nicer job in SS, AL, and brass than my big 2" B S compression
type, IMO. The cutting type of knurl is apparently a bit more
sensitive to the diameters and TPI than the forming type in
preventing 'doubling', but I haven't had a problem with my
particular sample of jobs. Lots of good info there on the Accu-trak
website, including answers to your other questions about straight
and diagonal knurling, feeds and speeds, etc. On the question of
bearing wear caused by asymmetrical knurling tools, there's no
question that you put a pretty good radial pressure on the spindle
with one of those. The large plain spindle bearings used in South
Bend lathes, *if* they have proper lubrication, are not usually
bothered by such pressure - but the smaller the lathe the more
potential you have for breaking through the lubricating film that
provides the actual bearing. Cutting knurls, and balanced forming
tools like the scissors and honkin' big U-shape straddle tools,
reduce this side pressure significantly. Mike (10076) |
| With
respect there is no way you can effectively "ram the knurling die
into the blank" using a 9 or 10 inch SouthBend. The crossfeed
leadscrews are far too slender and will simply spring buckle
slightly under the applied load. Ramming works fine on big machine
with a hefty feedscrew but it does have to be a solid push. Springyness just makes the original problem worse as any variation
in cutting force, due to material variations, out or roundness, chip
build up etc, will cause the knurl bounce in and out of cut
slightly! That said the lighter loads produced by the cutting knurls
advocated by Mike help considerably. I feel that, on small lathes
having conventional "push" cross feed screws, knurling (and parting
off) tools give best results when used in a rear toolpost. This
places a tension load on the feedscrew making everything far more
stable. Clive (10090) |
| Clive and all, With
due respect, ramming is exactly the technique I use to knurl
successfully. However, I think something may have been lost in the
translation. This is how it's done. Bring the knurls into contact
with the work. No rotation needed. Move the carriage to the right
putting the knurls in the clear. Advance the knurler for a cut. Now
start the lathe and move the carriage back to engage the work. This
is the "ramming" part. Beveled knurls are best for this. By having a
heavy feed at first forces the knurls (2) to track together most
times. If the first try was too light a cut and mistracking is seen,
roll back off the work, advance the feed and try again. Advance the
feed only off the work. Always allow extra material for the starting
area to be trimmed off later. The revs should be under 100 RPM and
the entire operation should be completed in as few a number of
revolutions as possible. Special calculations and diameters are not
ever required. The whole thing happens faster than you can read this
for perfect knurl. Oil is not strictly necessary but do keep the
knurls clean with a brass brush. My knurlers are shop made and only
the pinch type. RichD (10091) |
| Clive's comments
are good observations and worthy of discussion - the bare Accu-trak
quote could be interpreted to mean ramming the knurling tool
radially into the workpiece, and that's not what was meant, AFAIK.
'Ramming' is the effect when the knurling tool. already set for
correct engagement, encounters the workpiece as the carriage feeds
the tool towards the headstock. Based on a fair amount of knurling
on small ( 11") lathes, I think what they were actually trying to
get across is that there is no room for timidity. In setting up the
operation, you have to move the knurl(s) up to the point of
touching, then advance a combination of the forming dimension plus
compensation for any spring in the system. The latter is sometimes
the killer, because we often try to perform these operations on
slender workpieces without proper backup like a steady or follower
rest. Obviously the balanced tools like the scissors and U-frame
knurling tools have a lot less spring to factor into the mix. There
is certainly a degree of experimentation required for most
materials, and some sort of scribbling of what you've tried with
your lathe is a useful part of every enthusiast's bookshelf. With a
reasonably stiff workpiece, when you start the spindle and turn on
the carriage feed toward the headstock, the moment of contact as it
moves to the left truly appears like "ramming the die into the
blank." It's one of those things that seems to defy our natural
persuasion toward gentle treatment - but like parting off, too
little can be disastrous. It applies as much to a small lathe as
much as a large one, at least in my limited experience. (The largest
lathe I've ever used had a 14" capacity, so I can't speak for
anything larger.) The "ramming" is definitely a good description
with knurling in my Heavy 10, somewhat less so in the 11" HLV-H. I
wholeheartedly agree with the rear toolpost idea for parting off,
but I need to better understand the physics of the reaction forces
on a free turning knurling tool that would make a rear mount
preferable, since there is no "lifting moment" as there is on a rear
cutoff or turning tool. I need to noodle that one for a bit. I'm
already biased towards rear toolpost usage, but this particular
application needs further thought and trial. Unlike some materials
like concrete, steel has the same strength in tension as it does in
compression, but there may be some other reaction forces at work
here. Mike (10092) |
| I'm not going argue
if it can or can't be done on a small lathe with bushings. I'll just
state my technique which has worked perfect every time well almost
but it's the most reliable that I've found. Bring the knurls into
contact with the part angled slightly so the left side of the knurl
wheel will act as a lead in. you must do the following very fast to
get it right and you need some guts to do it. Turn the lathe on to a
med speed about 200RPM depending on your part diameter. As soon as
the lathe comes on dial in pressure on the crossfeed and rock the
carriage back and forth about .100" to .200" each way, this helps
seat the knurls. Once you have the knurl about one forth pointed up
stop the machine inspect the knurl to be sure you are tracking
properly if all is well set the feed to about .010 to .015 per rev
use oil or kerosene for steel or alum respectively. and hit the
feed. at the end of the knurl stop the lathe reverse the feed and
start the lathe back up. Now I've heard everyone's technique of
knurling but no one has said how to fix it if it goes wrong. using
my technique above if you don't get it right the first time you most
likely didn't push hard enough on the crossfeed. so pick a new spot
and try it again and this time push the friggin thing. Kerry (10096) |
| Humblest
apologies for forgetting that bevel edged cutting knurls can be fed
along in a manner similar to a normal turning tool and for not
realizing that this was what was meant by ramming. Obviously the
loads imposed are much lower and, more important, of the form a
lathe is best designed to withstand. Handwaving analysis suggests a
fairly significant longitudinal component (i.e. along the bed) to the
cutting forces which must help. I was thinking in terms of forming
knurls which need far more push into the workpiece. On a big lathe
straight in radial feed is perfectly practical but a confident
approach is essential for a clean start. In the words of my mentor
"Ram 'er in boy!". Hence the confusion. Attempting to use forming
knurls in this manner on a 9" SouthBend is not, in my experience, a
rewarding experience. However I have successfully used direct radial
feed with square edge forming knurls in a pivoting head type twin
knurl holder mounted in a rear toolpost. I put the difference down
to the better behavior of the cross feed screw in carrying a load
under tension than under compression. It is well known that slender
objects are much better at carrying loads in tension than
compression. As the feed screw cross-section is effectively not much
more than that of a 3/8" rod it hardly seems likely that it will
take the forces of direct radial knurling without trying to buckle a
bit. The Heavy 10 with taper turning attachment has a telescopic
cross feed screw pulling from the rear so it normally operating in
tension. Performance with parting and knurling tools in the normal
toolpost is vastly better than the other 9" and 10" models. Some of
this must be due to the heftier headstock spindle and bearings but I
think the tension mode screw helps a lot. The parting off
performance of my Heavy 10 is on par with a friends big 16" Harrison
which has a much heavier headstock and a conventional 7/8" crossfeed
screw. Clive (10097) |
| Knurling |
| Anyone have some
good tips on knurling? What feed rates should be used? How are the
diamond patterns rated? Bob (18240) |
| Run your lathe as
slow as it will go. Use plenty of oil, I use pipe threading oil, and
go back and forth advancing the tool in in very small amounts. Keep
going over the same spot until you get the depth you want. You need
different wheels for different size diamond patterns. Sorry but I
don't know how they're rated. Joe (18244) |
| Most important of
all the diameter of the piece being knurled must be a multiple of
the tooth pitch of the knurl. This is necessary because knurling is
a successive process of upsetting the surface were each revolution
upsets a very small amount and you must increase the feed of the
knurl as it makes its impression overtop of the previous revolution.
Search the web for Knurling and you will find many explanations and
procedures. Ted (18246) |
| Bob In the shop we
recently I bought a clamp type knurling tool that fits in the Aloris
type holders and you tighten onto the part instead of pushing against
the part. You can check these out in any of the MSC tool catalogs or
others. The only thing I can say is they are WONDERFUL. I would have
bought one years ago if I only knew how nice and easy they operate.
Watch the size range some are limited we found one that went from
near nothing to two inches and are very happy with it. Some we
checked out went like half inch to inch and a half . We have med and
coarse wheels and find that is all we need, probably could get by
with just med. Grumpy (18262) |
| Bob Starting the
pattern is the toughest part. As someone else pointed out, go very
slow and use lubrication. Make sure the tool is even with the center
of the work piece. I usually start the pattern turning the spindle
by hand. Start the knurl close to edge if possible or if it is not
near an edge, tilt the tool slightly so that only one side digs in.
This puts more pressure on a small area of the metal and will help
to get a good pattern going. Once the pattern has started you can
straighten the tool out, carefully re- engage the wheels and it will
follow the pattern you established. I have knurled many different
diameters using the same size tool so roller diameter is not a big
issue. Ron (18265) |
| As ever its a great
help to know your tool. Inappropriate tooling is a prime cause of
knurling troubles experienced by HSM types. There are two types of
knurls:- Those that primarily Cut the the knurl and those that
primarily Form the knurl by raising and depressing metal in
appropriate parts. I've never used Cutting knurls as these are not
easily available in UK. They are said to put much less stress on the
lathe but I believe that they need to be fed in from the side like a
normal cutting tool. Diameter of starting material is important with
these knurls as the raising and depressing of material is much less.
Forming knurls are (theoretically) fed straight in and put a lot of
stress on the lathe. Conventional holders have a bar carrying a pair
of knurls held in a floating pivot assembly so that they find the
work centre line automatically. On a lightweight lathe its best to
use them in a rear tool-post. On anything less than a Heavy Ten
trying to use them in the normal tool post tends to be very
frustrating as the lathe really isn't strong enough to generate the
high and consistent pressure needed on the work-piece. Standard UK
model engineer practice is to use forming knurls in a pinch holder
with the knurls held diametrically opposite one another in a pair of
pivoted arms with a pinch screw between them to apply the cutting
load. Much kinder on the lathe. Obviously you slowly tighten the
screw to deepen the knurl as the process proceeds. Can be tricky to
start with both knurls working together. Get it wrong and you get
the weird double knurl effect. It is important to have the knurls
accurately set on the lathe centre line. I have a very effective
hand held knurling tool which carries three matching knurls in two
against one formation on a pair of pivoted arms. The arms are
pivoted in front of the knurls and squeezed together like a pair of
nutcrackers. The pivoting arrangements allow you to adjust the arm
spacing to suit the work-piece diameter. These work very well on all
materials once the holding and traversing knack has been acquired. I
tend to run at either bottom direct drive or top back gear speeds on
the Heavy 10, mostly my knurled pieces are between 0.5 and 1.5 inch
diameter. The three knurl tool seems impervious to multiple starts
so, if I were to make or specify a knurling tool for a small lathe,
I'd use this format on a pinch type holder. It is often said that
"the diameter of the piece being knurled must be a multiple of the
tooth pitch of the knurl". For forming knurls this is something of
an "old fitters tale". For any relationship between knurl pitch and
work diameter that produces a job of aesthetically acceptable
appearance variations in the starting work-piece diameter merely
alter the height and depth of the knurl relative to the starting
body diameter. it also alters the amount of material actually cut
out by the knurls. Many years ago I had this demonstrated to me on a
heavy duty lathe. I would not however care to apply the feed loads
used on any lathe of mine! With a small lathe its best to minimize
the loads applied by the knurling process and starting near the
correct diameter will be a great help. Do remember that the knurl
will settle into cutting the pattern which needs least effort.
Starting a fraction under theoretical diameter might be better as,
with two knurls, if its exactly on diameter a double knurl pattern
is just as "easy" as the single pattern. Obviously the three knurl
tool suffers much less than a two knurl one from this sort of
problem. Clive (18268) |
| I would agree with
all that has been said. On a small lathe the only knurl to consider
is the "pinch" type. I have received consistently better results.
(18269) |
| While we're on
knurling, I cannot figure out how to make a single (not diamond, but
straight across) knurl. I bought a single-wheel knurl with straight
teeth on the wheel, but this is crap. I work mainly in brass and
aluminum and with little parts, so I don't have the feeling that I'm
overstressing the cross-feed on my 10k, but will, some day try the
pinch-type knurlers. But any advice on making straight knurls much
appreciated Frank (18271) |
| Knurling
question |
| What is the
diameter tolerance on knurling? Lets say you have a .955 dia bar
which is 3" circumference (to keep the math easy) and a 25 lpi
diamond knurl (.04") This should generate 75 lines per
circumference. The diameter should be a multiple of pitch/pi
(.04/3.14...)or multiples of .0127" to get a clean knurl. How much
can this diameter be off and still get a clean knurl? For a 14 lpi
knurl the diameter should be in multiples of .0227" How much can
this be off to get a clean knurl? Is the diameter tolerance for a
straight knurl more or less critical? JP (18483) |
| If you have
Machinery's Handbook it contains tolerances of diameters for
knurling. If you don't then for 75 lpi the table shows a tolerance
of +/- 0.001 to 0.0015 for the least critical class of knurl (class
I and II). For high class (Class III) tolerance is + 0.000, -
0.0015. Ted (18484) |
| Phase 2
knurling tool |
| What is the size is of the knurls on their AXA equivalent tool holder,
I come up with 1.6mm Is this correct, I can't find any catalog info
other than med knurls. (18495) |
| That's only 1/16".
Do you mean 16 mm? (5/8" diameter) Usually the problem is matching
the bore and width size. BTW, all that fussing with diameters is
hogwash. Kurling any diameter with any knurl set is a simple
technique. Use bevel edged knurls set dead square with the stock.
Very slow speed and use as few revolutions as possible. Start from
the edge after touching the knurls on the stock. Close the knurler
slightly and run onto the stock slightly. Check for tracking. If not
close more and try again. A heavy feed from the start will almost
guarantee tracking. Slowly run across the stock and run back off.
Close the knurler only off the stock. Do again if needed, but do so
in as few revolutions as possible. Don't over do it. RichD (18497) |
| I went to the Phase
II website at http://www.phase2plus.com and then to the page on the
knurling tool. It says the size is 3/4" X 3/8" X 1/4". Dave
(18499) |
| I was referring to
the cutting pitch. I ran it against a piece of well oiled stock just
for the hell of it. The stock was approx .935 and it produced 46
clean diamonds around the stock. The pattern was not full depth, it
was only .01 to see how the tool worked, I expected an odd cut, not
a clean one. I am not quite sure of the starting diameter because I
used an old caliper that was handy, not the known good one. I
figured it was probably 14 lpi which is common, it calculates to be
15.66 or so. The closest standard knurl I found that is close is
1.6mm and with that the stock should have been .922". I went to look
up the pitch of the tool and hit a dead end. So I ask, what is the
pitch supposed to be? When I went looking for metric knurls I found
15 degree as well as 30 degree and straight but no female knurls,
metric or imperial on a quick search. JP (18502) |
| I found info on
knurling at
www.doriantool.com/Knurling/Knurling_Catalog.pdf There
is info in here on straight knurls, someone asked about that a while
ago. What I was looking for is on page 14 optimum blank diameter and
correction factor. Technical info is the first third of the catalog,
tooling made in the USA. I measured the Phase 2 knurling tool and
found 37 teeth on 3/4" diameter which comes out to 1.6mm transverse
pitch. I called Phase 2 and asked what the pitch is and the person I
spoke to didn't know and couldn't find the info, what an outfit!
Tooling made offshore. JP (18525) |
| Decent Knurling
Tool |
| JP I find the hand
held, hand squeezed, three wheel "nut-cracker" type tool very good
for virtually all my knurling. I've got tool post mount types
somewhere but have not used them for so long that the little man who
lives under the bench probably had them away sometime in the last
decade. Unfortunately these seem very rare but can be made quite
easily. I've got some DIY drawings for one which is a dead ringer
for mine somewhere and could easily e-copy them to you if you are
interested. Clive (22722) |
| I've
sent details and pictures of this 3 wheel hand held tool off list to
everyone interested. If I've missed anyone out E-mail me direct and
I'll rectify the omission. I think putting details in the files
should be done by some-one who actually builds the tool. I'm not
convinced that an almost direct copy of the commercial one is the
way to go for HSM types. Some things that are easy in a factory are
hard for us and viky versa. To the best of my knowledge this tool
went off the market in the mid 1970's so some small changes, e.g. to
knurl sizes, to reflect what is currently available inexpensively
may be sensible. I've only ever seen two, one at work and one in the
"bin box" at the tool supplier I bought mine from. It cost me "50
pence for the knurls mate 'cos its obviously a rubbish tool".
Despite knowing better I kept big mouth shut and paid with a smile.
Good day that as I got a South Bend 9" Model A, literally fallen off
the back of a lorry resulting in damaged handles, for œ50 and a
discount on the big pillar drill I went to buy. Clive (22758) |
| This thread
has sparked off a bit more interest than I expected even though
knurling is right up with parting off at the top of the least
favorite job list. I think everyone wanting them now has copies of
the drawings and pictures. If not please e-mail me off list. One
thing I have found is that its much easier to keep track of this
sort of distribution thing off-list rather than running through the
digest. Putting it in the files seems a popular idea but we really
should re-draw, verify component availability and modernize (if
necessary) first. Seems sensible to aim for middle of next year to
put a SBLG version up. I'm happy to act as contact guy for mods,
suggestions and experiences so if anyone who builds it, uses it or
has comments on the design "from making something with a similar bit
in it" would care to e-mail me we will sort out a proper job that is
also easy to make. Clive (22778) |
