| 9" Gib Screws (Sep 7,
2001) |
10 K carriage gibs? (Jul
28, 2002) |
| Gib Screw Adjustment (Sep
25, 2001) |
Making Gibs: Can anyone share
some experience? (Feb 10, 2005) |
| |
| 9" Gib Screws |
| Does anyone know of
a source for the gib adjusting screws on the 9" cross-slide and
compound. They appear to be 10-30tpi which of course is not too
standard. Sure appreciate the help. By the way I am a new members
and on my second 9"S.B., this one a 9'x4 1/2'A. It's an ex- school
lathe, went through two owners before me, has lots of the usual 'school' marks
but has surprisingly little wear. The spindle to tailstock droop is
only 0046" and about 0008" spindle clearance which indicates some
shim adjusting may have been done. Ray (1482) |
| The gib screws are #12-28 (if
memory serves me right). I don't know of a source for them off the
top of my head. You could by the die and make them yourself. If
anyone else know a source for these, why don't you pipe up! Webb (1487) |
| My local hardware
will have them-- its kind of an unusual hardware. Yasmiin(1489) |
| One thing I noticed on the gibb
screws of my 1942 vintage model B was that those screws are on the
fat side by a thou or so. I would assume they did that to keep them
in place. (1492) |
| Brownell's has
#12-28 screws if I remember correctly. I doubt that they can be
found in many hardware stores. Kim (1493) |
| Gib Screw
Adjustment |
| The
cross feed on my 9" 'C' is a little tight and I would like to adjust
the five gib screws on the compound rest to free it up little. Is
this something the untrained (me) can do, easily or does the gib
adjustment affect the accuracy of the cross feed travel? If it is
simple adjustment is there a sequence for each of the five screws
(front to back, back to front or centre out? Are feeler gauges
required and if so how much play is acceptable? Bill
(1591) |
| I was just reading
George Thomas's book Model Engineer Workshop Manual. In it he states
plainly (and surprised me) that the cross slide should be freely
movable by hand (if the lead screw has been removed or loosened).
The idea seems to be that a smooth moving slide allows that 1/2
thousandth feed you might want now and then. On my SBL 9, I remove
the handle (watch out there's a tiny dowel inside), and the dial.
This frees the cross slide. Clean and oil the slide, loosen all the
gib screws. Tighten a screw until it stops hand movement of the
slide, back off just a hair - the slide should still move. Do for
all the gib screws. Reassemble. You now have a small problem, if
there is any chatter the cross slide is gonna move! George Thomas
recommends drilling a new hole for a locking screw and handle -
which I will do soon. Meantime, I remember where the screws are set
and will tighten one down when I want to lock the slide. I am not a
pro, so interested in hearing comments from the "real" machinists in
the group. Bill (1596) |
| Bill and Others,
The way I adjust the gibs on lathes with "standard" gibs (as opposed
to tapered gibs) is to first separate the sliding member from the
stationary member (relatively speaking). The reason for this is to
allow you to clean and deburr the dovetail ways so that you will get
a better and smoother adjustment. Also check that your gib screws
turn without binding. This is important and makes adjusting much
more easy. After you have cleaned and deburred, oil and assemble the
sliding member back onto the stationary member. Turn each gib screw
in until it is tight and then back off 1/8 to 1/4 turn. Then slide
the sliding member back and forth a few times. This will help the
gib to seat properly. Now for the real adjustment. Starting at the
center screw, tighten the screw until the slightest pressure is felt
from its contact with the gib. Check the sliding member's free
movement. If the sliding member has any friction, loosen and tighten
again (but not quite as much as before). Repeat this until the
member slides freely but has no side to side play. Repeat this
process with the other gib screws working outwardly, in a sea-saw
left to right from the center screw. You may have to repeat the
whole process a couple of times to make sure the gib is seated
properly. Now for some caveats. The cross slide dovetails wears
unevenly; having more clearance at the crank handle end. You may
find that your sliding member binds as you crank the cross slide in.
In that case, adjust the gib when the sliding member is at the end
of its "normal" travel (not the end of its total travel). This will
allow it to be correctly adjusted for where the sliding member does
most of its work (of where it "lives" if you like). Another caveat
is when the gib is bent or warped. This gives a false sense of when
the gib screw contacts the gib. Ideally, you want the gib screw to
contact one side of the gib, just as the other side of the gib
contacts the dovetail way. Otherwise, the pressure on the dovetail
way is uneven and increased wear is the result. A slight warp or
bend is not too serious but a true flat gib is best and is the
easiest to adjust. New gibs are not hard to make and if you have
access to a surface grinder, you can make (or true-up) a superb gib
in no time. Webb (1615) |
| I
adjusted the compound rest gib screws last night, following the
advice from Bill, Webb and Ron. I
leaned more towards Webb's process as it didn't involve removing the
cross feed screw. There is enough area on the CR to make a
reasonable adjustment without removing the CFS, although I'm sure
removing it would be preferable. The whole process only took an
hour, including removing the gib screws and cleaning and oiling the
whole CR. My cross feed is now smooth and bind free!
Bill (1641) |
| 10 K carriage
gibs? |
| I have a
10K South Bend lathe, (Catolog# 370 ORD, Model # 344ZN) The lathe is
in very good shape, but I can grab the apron and lift up on it and
the entire saddle lifts off the ways at least .030"! If I snug down
the saddle lock it solves the problem, but it seems to me that there
ought top be a gib of some kind to control this clearance. On the
back of the saddle there are two bolt coming up thru the bottom of
the saddle that clamp against the bottom of the rear way. There are
no lock nuts on these to maintain their position, but they do allow
you to adjust the clearance at the rear of the saddle. I have not
been able to find anything (other than the saddle lock) to
accomplish this at the front of the saddle. Mario
(5439) |
| What you see
is what there is and what is needed. I usually run with the carriage
lock about 1/4 turn loose. Your cutting loads will push the carriage
down on the ways in the front and try and lift the rear, so the rear
needs to be adjusted to be just smooth. There is no adjustment in
the front because none is really needed unless you are going to try
and run inverted tools in the front tool post with the lathe running
in reverse. JWE (5442) |
| Jim, I
agree that, theoretically, all the cutting forces are down and you
shouldn't need anything to keep the carriage from lifting up.
However, I can see that, if you are taking a reasonably heavy facing
cut on fairly large diameter work, (where the cutter is outside of
the lead screw) you might see a problem. The primary force on the
cutter is, as you say, down, but there is a fairly large component
away from the work (towards the tailstock). It seems to me that if
you have a force acting along the lead screw, or the rack above the
lead screw pushing the carriage toward the headstock and a force
acting outside of the leadscrew (toward your bellybutton) in the
opposite direction, the carriage would tend to want to rotate or
"yaw". Obviously the Vee ways resist this rotation, but if the
rotational force got high enough and there s nothing to hold the
carriage down, the carriage could start riding up the Vee way! All
right, maybe I'm getting carried away but I agree with you
about taking advantage of the carriage lock. Thanks for your reply.
At least I know I'm not overlooking something obvious. Mario (5448) |
| JWE, et al, As we
had discussed, theoretically, there should be no need to restrain
the front of the carriage from lifting up since all the cutting
forces are down. Last night I was boring a small dia. deep hole (3/4
x 2.50") using a Bokum boring bar that was not much smaller in dia.
than the hole. I was getting a some chatter (not unexpected for that
dia. to depth ratio) so I started looking at and feeling things to
see what was happening. I noticed that the whole carriage was
jumping up and down...I don't know how much, but I could see it. I
immediately reached for the carriage lock and tightened it till
there was a slight drag and it improved considerably. The chatter
didn't go away, but it did get better...and the carriage stayed where
it belongs. I'm still not sure exactly what was going on, but I
think that either the chatter of the boring bar was pushing the
carriage up and down, or, more likely, some swarf was getting jammed
between the back side of the boring bar and the bore opposite the
cutter...where the bore is moving UP with respect to the cutter, and
thus lifting the cutter. By the way, I finished up with lots of
float cuts and then a reamer! Any suggestions on how to
minimize problems in a situation like this? Mario
(5510) |
| Mario, I have the
same problem with my CNC Compact 5. Not to bad with OD work, but ID
work really shifts around the carriage. You didn't mention what type
of material you are cutting. I am mainly cutting aluminum 6061 T-6.
I use inserts by H. B. Rouse. They are for Aluminum. I do notice a
bit better performance. They helped, but I still have problems.
Mainly, I'm running too large of parts for this machine. I would say
that with a boring bar you have an extra force acting on the
carriage. Since the B-Bar is extended out, the forces would try and
pivot or rotate the carriage. Keeping the B-Bar as short as possible
is all I can come up with. My solution to this problem was to get a
bigger CNC lathe. It hasn't gotten here yet, probably next week.
Also, let us know type of B-Bar, material and type and grade of
inserts used. Tom
(5511) |
| Tom, The only
solution I have found is to bore shallower, larger diameter
holes!?!? Just kidding. I did forget to mention that I was
machining mild steel. I am not using an inserted boring bar. I am
using a Bokum boring tool which is a solid high speed steel boring
tool. They generally cut very well but this is such a small dia. and
cantilevered out like that I'm not sure what else you can do. I
think the tool was nice and sharp, but I guess I could touch it
up with a stone and see if it helps. Tom. (5512) |
| Mario, I don't have
any experience with a Bokum boring tool. I also don't know your
machining experience. I would say check to make sure the tip of the
cutting bit os on center. Also, try and use as small a tool nose
radius as possible. This will put less pressure on the tool. The
down side to a small TNR is accelerated tool wear. So if your not
hogging out a lot of material, it should be ok. I should not that
smaller holes are more sensitive to the center height of the tool,
just as smaller OD diameters are too. I'd probably put as much side
clearance on the tool as possible. I don't know if you are flat
bottoming the bore or not. If so then drill with a Flat Bottom drill
and have at least 3-5 degrees clearance on the front of the tool.
Just remember that clearance comes at the price of tool strength.
Tom (5526) |
| Tom, All very good
advice. The Bokum tool are ground with a minimum nose radius (less
than .030"). The more I think about it, the more I think your advice
about center height is the most relevant. I suspect I haven't been
as careful as I should with setting it. I probably ought to get out
my surface gage ands set it accurately and see if it makes a
difference. Regarding my machining experience, I'm not a total
novice, but I don't have a lot of experience either (never worked as
a machinist for a living) so I will gladly accept all the advice I
can get. Mario (5527) |
| Mario, You might
think about trying .015 to .008 TRN. I don't know if you have a QC
tool holder or the 4 Position type ect. On a manual lathe, I try and
use the a dead center in the tailstock to set the tool height. With
an Aloris type, I can't say how easy or hard it will be. Also, as
far a feeds and depths of cuts. The feed should not be more than
your TNR for a good finish. The depth of cut should be a bit more
than the TRN, actually twice that due to taking material off both
sides. I hope you follow that, you would more the tool out say .020
actual movement for a .015 TNR. This would open the Diameter .040. I
constantly ignore this rule though, and take skim cuts. But the
finish isn't as nice. Tom
(5528) |
| Are any of you
familiar with using either a 6'" ruler or straight bit of hacksaw
blade held between the tool and the work to set it to height? if
when you press the ruler between the tool and the job the top of the
ruler moves away from you the tool is too high if towards you too
low. You need to get the job in the chuck turned to be concentric for
the scheme to work really well. For carbide tips allow the tool
holder to swing or you may lose its edge. Phil (5531) |
| Phil, I have used
that with OD tooling. I guess you could use the back side of the
part for ID tooling. Tom(5532) |
| Phil, Good point. I
always thought of that technique when turning o.d.'s but now that
you mention it, I guess, in most cases, the i.d. and the o.d. are on
the same center! Duh!?!? Mario (5533) |
| I don't know what OD
tooling is, tell please? Phil (5534) |
| For the I/D turning
use the rear of the job to rest the ruler etc against. Phil
(5535) |
| Phil, OD = outside
diameter, so regular tool holder. I think I have tried to use the
flat stock method a time or two for ID tooling. If I remember, the
Diameter of the part was more than I could move the cross slide to
get the B-Bar on the other side of the part. Still should work most
of the time. Usually, I face the part and setup on the center swirl.
Tom (5536) |
| Not splitting hairs
but I am used to O/D and though that OD was some proprietary gear,
People divided by the same language. With carbine tipped tools you
need to be with at least say 0.002" or 0.01 mm of centre height or
disaster and cost will follow. Phil (5537) |
| Phil, When I used
the term 'OD', I simply meant 'outside diameter', That's the danger
with acronyms... no matter how obvious they may seem to the user! I
guess we need to remember that WE always know what WE mean, but the
one we are explaining it to may not! Mario (5549) |
| Making Gibs:
Can anyone share some experience? |
| My
old gib isn't sliding well, so I am trying to isolate the problem.
So I would like to either LAP the old gib, which isn't in perfect
shape, or MAKE A NEW ONE out of either steel (what kind?) or
BRASS ( is this a good idea? ) I have some ideas as to how good an
idea brass is, but I would like to hear what you guys have to
say. Bernie
(25061) |
| Steel, low carbon
cold rolled C1018 is the easiest to find but anything with a C10XX
designation will work. Brass is not a good idea up against cast iron
at any time, bronze is worse. JWE (25063) |
| Bernie For our
levels of use the specific grade of steel is not terribly important
but go with JWE's advice if you possibly can. What is important is
that it be flat, parallel and capable of taking a good surface
finish. I assume you are planning to make a conventional side screw
adjusted gib. (Taper gibs are a much harder proposition for
machinists unless you have all the proper gear although it is
possible to do a superlative job by hand using adapted optical
workers techniques.) If you are going to make a gib you will get
much more benefit from the effort if you take time to carefully
overhaul the slide and pay attention to the extra details which make
the difference between a "Well its better than it was" job and one
that is beyond reproach. I'll send you something off list which may
help you but, summarizing, the important points are:- 1) Verify that
the working surfaces on the slide itself are still true and lap
lightly if required. 2) Break all the sharp edges and scrape out the
corners. 3) Check that the thrust surfaces for the feed screw on
both slide and screw are in order. Rectify if required and, if in
bad condition, consider adding a thrust bearing. I don't think a
roller thrust will fit but anti-friction dry bearing material coated
washers are worth considering. 4) Make the gib strip from material
thick enough to be a smooth sliding fit in the gap, a "couple of
thou" clearance is ample. 5) Take pains to get the top bevel angle
just so, the strip should sit properly up into the top of the gap.
6) Use a centre drill to produce smooth conical seating for the
adjusting screws, best to use the slide to jig drill for accuracy.
7) Refurbish or make anew the ends of the adjusting screws, ideal
shape is hemispherical so that they bear on the sides of the seat
dimples. Sharp points bearing on the end in a curvy dimple will
never work well. Best are hardened ball ended screws, but they are
the devil to find. I consider that its well worth the extra effort
to add a dowel through the slide and gib strip preventing any
sideways movement. I would also add an extra adjuster screw with a
thumb lever so that you can easily lock the slide or add a bit more
drag when doing heavy or interrupted cuts. The accumulation of wear
on ageing lathes means that its often necessary to have the gib a
bit tighter than desirable for easy, accurate adjustment in order to
ensure that it stays where it is set on heavier jobs. The slide lock
screw neatly resolves that problem. After refurbishment lubricate
well with a proper slide way oil and set-up with the feed screw
removed so that you can feel exactly what is going on when you slide
it backwards and forwards. Having made a good job of things you will
find that the adjusters can be much tighter than previously before
the slide becomes tight. This extra tightness translates into a more
rigid set-up which is a Very Good Thing. Clive (25077) |
| WOW!!! Clive I
can't thank you enough, and this is just the kind of information I
am looking for. I have a "big" Southbend coming next week, from
a friend who is enjoying my interest and wants to help me. I am
working on a small Atlas lathe right now, and have come quite a long
way, without kidding myself, towards making a more "real" machine
out of it. It will still have limits as regards the strength of the
castings and its size, but I can do things already with the machine
still acting completely tame and steady that were impossible
before. When my "BIG" SouthBend next week, I will be happy to see
what I can accomplish with that! Any information you can send me
off-list will be accepted with great appreciation!! I'm printing
this message out and getting to work! Bernie (25086) |
| Mine are made from
1/8x1/2 CR steel. They are flat with just the angle's cut on the top
and bottom to match the height of your dovetail. Pretty simple if
you have a mill. Bob (25087) |
| Is yours the
standard cross slide? Mine, 10K, has the tapered gib with the single
adjusting screw, fortunately both it and the compound are in good
shape. Otherwise I guess it would be on the mill with lots of fiddly
packing to get the taper, very light cuts followed by a lot of
lapping. Bernard R (25093) |
| Actually mine is a
replacement T slot cross slide by MLA. Machined by Earl Bower. I
will have to look at my original one. Bob(25094) |
