10L tailstock alignment

Is there more to getting a 10L in reasonably good shape to turn "true" over a fair distance (about 10 inches in this case) than alignment of the tailstock with the headstock? The bed is in good shape, somewhat sorn near the headstock (as measured in terms of thickness the bed is about .005" thinner near head than tail); someone said in a recent post that he can turn to within .001" over several inches with a .015" ridge in the bed of his SBL. Mine has no ridge whatever. After fooling with the tailstock with a dead center in it and a dial indicator stuck to the chuck via magnetic base was able to get within about .003" over 10". Pretty close, but not really good enough (started out with about a .015" taper, and after aforementioned fooling got it down to .003"). What's required? More fooling? What don't I know? (poorly phrased question; answer: a lot!)

1) get the bed trimmed first *without* using
the tailstock at all. Use the two-collar
method as the SB booklet describes.
If it is an older cast-iron base machine you
will need to shim the tailstock end legs to
do this, if it's a newer machine then there's
a bed twisting screw setup at the tailstock
end.

2) only once you can turn to a thousanth
or so over five or ten inches near the
headstock should you go and try to tweak
in the tailstock. Check that it's at the
correct height and that that it is parallel
in the horizontal plane to the bed surface.
This can be corrected with shim between the
two tailstock halfs.

Then you can use the front/rear adjusting
screws to bring the ram in line with the
spindle axis front to back.

Jim

Ok, forgot about leveling it. Book (How To Run a Lathe from SB) shows levels across the ways "front-to back" if you will. Is level from headstock end to tailstock end as critical? No mention of this in "The Book" that I found, but my floor definitely has a pitch to it in that direction. What I mean is, if the bed is level (not twisted), how critical is it that the machine is level in the other direction, or on the other axis?

Flat is more important than level. I think what Jim is getting at is making sure the feet out on the tailstock end are shimmed so the bed isn't twisted along its length. Unfortunately, a carpenter's level isn't sensitive enough for this measurement.

Gregm

There is no need for any level. Simply
turn a piece of stock in a chuck, and mike
both ends. If the diameters at the chuck
side and the outboard side are not the
same, you need to adjust the bed by
either shimming the legs or tweaking the
bed twist screw, depending on the vintage
of the machine.

Jim

Jim, how do you differentiate between a twisted bed and a misaligned tailstock, since both will cause a taper? In other words, applying the method you describe, how do know a taper requires untwisting rather than tailstock adjustment?

You need to set the machine up to bore and
turn true, without any tailstock center first.

That will leave the bed in the best condition
you can - you will have replicated the condition
when it was originally set up at the factory.

Only *then* can you consider investigating how
the tailstock ram alignment looks - by first
inspecting for axial alignment to the headstock
spindle, and parallelism to the ways.

The ultimate test of course is to put work
between centers and turn a cylinder. The final
fore-aft adjustment of the tailstock offset is
then done to make the cylinder thus formed
the same diameter at both ends - a true cylinder,
not a cone that is a few thou larger at one end.

Notice that I said "between centers."

Putting the workpiece in a chuck at one end
and in a center at the other end, can often
give contradictory results. It is often done
as a matter of convenience but in the end the
geometery is over-defined. For the purposes
of checking to see if the tailstock setover is
correct I think work between two centers really
is best.

Jim

Well, I leveled the machine last night using a machinists protractor w/ a level bubble... the SB book says to use a machinists level sensitive enough to indicate a .003" change over 12". I couldn't find a .003 shim, but a .005" shim under the level was readily seen, and I got the machine pretty near on the money using that. I don't have the chuck yet, so I couldn't put a test piece in the headstock only, but I did put a test piece between centers (before and after shimming) and made a marked improvement: .020" taper before, .009" after. I should have the chuck in the next couple of days, so I'll turn the 2 collars like you suggested. Based on your first reply, I should do this about 5" from the headstock? Also, my only chuck is a 3-jaw; I have been told this is, bar none, the most inaccurate variety (I question that... a 2-jaw came in the misc pile of stuff w/ my Atlas that i'm sure will give any 3-jaw a run for it's money). I have also seen posts that said the "only" chuck is a 4-jaw (which I do not posess at present). What of this? Thanks for all the help so far.

Hi There,

The 3-jaw chuck may not be the most accurate work holding device, but for the "two collars" test, it will be perfectly adequate. Just use a piece of stock that is big enough in diameter to minimize defection of the work from the tool bit during machining. As long as you do not remove the two collar test bar from the chuck (or remove the chuck from the spindle), the test bar, when machined, will give a true indication of alignment.

This alignment test is primarily a test of the headstock alignment with the ways of the bed. A long two collar test bar held between centers will give an indication of how "flat" the bed is, provided that the tailstock is in line with the headstock. Otherwise, this test will not work correctly. You won't know if your chasing "wind" (a twist in the bed) or misalignment of the tailstock with the headstock. If you have a dial indicator set-up, you can mount it in the 3-jaw chuck and indicate the tailstock center to check tailstock alignment. Tailstock bases wear and sometimes this wear can be significant; causing the tailstock center to be low in relationship to the headstock center. So your alignment problems may not just be in-and-out alignment but up-and-down alignment as well (Sorry to be the bearer of bad omens).

Go ahead and run the two collar test with your 3-jaw chuck and report what you find. Got to go....

Good Luck!
-Blue Chips-
Webb

I left my shop after about 3-hours of trying to align the tailstock & headstock in utter frustration and headed for the PC to ask the same question, northeastconfederate. Nice timing !!

I tried using the 3-jaw that came with my lathe, but there's almost .010" runout in it. I then switched to my 4-jaw, trueing the test bar up within .001" at the headstock, using a .001" one inch travel dial indicator. I've been taking a full length cut (1.250" diameter bar, 13" long) and micing both ends, then shimming the tailstock vertically and resetting the offset horizontally after tramming the bar both on the side & top, trying to get everything aligned. closest I came was around .014". Maybe it's bed twist.

I'll go back to "square one" tomorrow, checking the level of the lathe and proceed on from there. I'll let you guys know if I was successful or if there's a 13" SBL up for sale

One question, if I may: My lathe is a circa-1949 model. Would this machine have the "bed-twisting" adjustment mentioned above and, if so, where would I look for it?

Is there another book I should get which is more specific as to maintenance on my machine, other than "How To Run A Lathe", which I did obtain & read ?
Thanks for your help,
-Bob

ChipBed, you are in for a long, interesting
session if you start by trying to turn between
centers.

Why not do the two-collar test that SB suggests?
That's the first alignment technique you should
perform.

What kind of machine is this? Does it have
the cast iron motor base, and two legs on the
tailstock end of the bed? Or is it the cabinet
type, with either the rounded pipe legs or
the sheet steel cabinet?

If the first, you need to put shims under the
tailstock end legs. I used 0.030 aluminum
sheet for my machine, that was a fine enough
adjustment.

If it is a newer cabinet machine, you need
to look at the tailstock end of the bed again.
There is a support that rests on the cabinet
and holds up the end of the bed - a separate
casting that is bolted in there.

There will be a small cover that obscures a
hole in the casting, or if the cover is missing
there will simply be a screw visible inside
the hole. There is a similar screw inside
a hole on the rear side of this casting.

The bed has a tang that drops down into the
support casting, and the two screws bear on
the tang front and back. By loosening one
of the screws and tightening the other,
pressure is applied to the tang which effectively
twists the bed around its long axis.

I know my steel cabinet 10L has such a bed
adjustment, but have never seen one of the
round pipe leg machines up close to inspect for
the same feature.

Anyway this is the adjustment that the
manufacturer wanted you to use to make the
machine turn straight and true. That's why
they put it there.

Jim

Hello all,
I shimmed the legs (I have the cast base, and cast legs arrangement) last night, as I mentioned earlier, then rechecked this evening when I got home to see how much it settled. WOW! First of all, I can't believe how far out my concrete floor is, and second, how much the lathe settled. I took about3/32" out in 2 places (both on the same side of the machine). What floors me (no pun intended) is that all 4 legs seemed to be firmly on their shims last night. At least, I couldn't move them by hand. Guess this is going to be a slow process.
An aside, for curiosity's sake I emailed LeBlond to find out when the machine was made, and it's a 1942 model.

This is very interesting because I have a 13 inch lathe made in 1969, and after reading your post, I checked it and it has the exact adjustment feature that you are talking about. The part below the bed you are talking about is called the oil pan short leg in the SBL parts manual, but the manual doesn't show the adjustment screws. The last edition of How to run a lathe from the 60's doesn't talk about this either. I have never adjusted mine, and my lathe seems to work fine. I use those rubber anti vibration feet with the adjustable nuts and put them in the holes in the castings on the bottom of the lathe. Then I use my machinists level to get the lathe as level as I can, then I make the test cut in the chuck, and make any additional adjustments needed. They seem to do a good job of leveling the lathe and allowing me to be accurate. The thread on mine are 16 TPI, which means a full revolution would be .0625, but rotating the nut just 10 degrees would be under .002. Anyway, they seem to work for me.

KrisG - if your machine has both the cast iron
legs, and the bed adjustment screws, they are
kind of redundant.

In that case I would probably slack off both
screws, and let the bed find its relaxed spot,
and then bring the screws in from both sides
with equal pressure.

Then I would proceed to level using shims under
the cast iron legs.

Jim

jim rozen,
You're exactly right and I will, of course, go back to the basics and use the 2-collar method after making sure the machine is level. My SBL is a 13", circa-1949 vintage machine. It has cast iron legs under the tailstock end and cast iron motor cabinet / base.

The lathe is set on approx. 3/8" vibration pads under the front & rear of the motor base and each of the legs under the tail stock. I have no accurate level and didn't place any shims under the tailstock legs. I can see now, I'll have to beg, borrow or steal a good, accurate machinist's level, before doing anything else. I'll try the .030" shims under the t/s legs as an interim measure.
Thanks for your comments, they're appreciated.
-Bob

Hi There,

Have any of you considered trying the Rollie's Dad method of checking lathe bed alignment?

http://www.john-wasser.com/NEMES/RDMLatheAlignment.html

This is the method of bed alignment used where the use of a level is not possible (like on a ship).

I prefer using a precision level myself to check the bed for wind (or the Datum Plane as Connelly refers to it in his excellent book: Machine Tool Reconditioning ). The two collars test in the chuck will work provided that the headstock is still in alignment with the bed. Otherwise, you are just exacerbating the problem. If you know that your headstock is in proper alignment with the bed, then you are fine. When SBL wrote those instruction, they were referring to a new lathe; that is, a lathe that they knew had no wear and all parts were in alignment when it left their factory. But these older lathes have had a life before you got it and who knows what has been done to them. Their past might be checkered at best. There are three things that can be the cause of failure during the two collar test in the chuck. Foremost is the bed is not level (or flat if you prefer). The other possibilities are wear of the prismatic ways causing wind or the headstock is no longer aligned with the bed. Leveling the bed is the best way I know of to check for bed twist and eliminating that possibility.

Go ahead and try the two collar test in your chuck. Just keep an open mind.

Good Luck!
-Blue Chips-
Webb

ChipBed - that is nearly exactly the way I had
set up my original 10L, which like yours had
the cast iron pedestal base, and the cast iron
legs at the outboard end of the bed. I also
used some composite rubber/aluminum anti-vibration
mounts, two under the motor pedestal, and one
at each leg. In my case I was bolting the
shims (I think they ranged from 30 down to
beer-can size...) between the leg and the pad.

This worked great and was the only thing I had
to do to get the machine to turn as well as it
did. It was a badly, badly worn old machine but
was great for what it could do. Because the
bed was worn I could not get it in to better
than a thou of accuracy within six or so inches
near the headstock - this using the two-collar
method.

Webb - of course you are correct. A used machine
can have had all *kinds* of abuse heaped upon it
and your caveat is well taken. Even so, all
the complete machines I've ever purchased are
taken apart for cleaning and a quick look-see.
All of the lathes have had the original hand
scraping visible on the bed under the headstock,
and the headstocks are fitted to the bed without
any interference from dirt, etc. which would
skew them off axis.

Your point is so important and vital, it bears
re-iterating in a stronger fashion so I would
do that if you don't mind:

I would personally *not* purchase any lathe that
has had the manufacturer's original fitment of
the headstock to the bed altered or destroyed.

Once this occurs the machine is badly compromised
and will probably never be accurate enough to
turn to better than a thousanth, over any length
along the bed.

If a machine were presented to me in that fashion,
the thoughts that would run through my mind would
be, "parts machine," or "hand scraping exercise,"
or maybe "scrap metal."

There are enough used, good condition machines
available that a machine with the headstock
tweaked up would have to be a) nearly free, b)
close by to inspect, or c) some unusual, vintage
lathe desirable as an antique. But *not* a
runner.

Jim

Hi everyone,
Made the last (I hope) shimming adj. tonight.
was perfect last night, then headstock end settled
and needed .025". T-stock end was still perfect until I corrected h-stock end. Checked again after 4 hrs, still off a few thou. Don't know if it needs more shimming or more waiting... I'm waiting. Let y'all know how the 2-collar test goes over the weekend. I also printed Rollie's Dad's method, but no sense changing horses in the middle of the stream. Just how long does it take for a lathe to take it's new shape anyhow?

Chip Bed- Those vibration dampers you mentioned could be the cause of the constant settling,if they're too soft. I would deep six them.
As for alignment, my practice is to level the bed the best you can,(I once came across an old gunner's quadrant at a surplus store). Next, bring the tailstock close to the spindle and with an indicator in the headstock align and shim the tailstock with the lock on. Worn t-stocks can shift when locked. Then using the two collar method, preferably between centers, make your test cut. Make your final adjusment by mounting the indicator on the carriage with the tip on the straight part of the center or on the ram, and shift the tailstock one half the difference between collar diameters. This should bring you pretty close to parallel. Repeat the last adjustment if necessary.
If you chuck your shaft instead of working between centers, chuck it as short as possible to avoid influencing the cut.
Good luck, Chaz

To re-iterate, the bed must be made true before
*any* adjustments are made to the tailstock.

The two collar method works well if you do not
have the ultra-precision level that reads down
to 0.001 RCH. Lots cheaper too!!

Jim