What's new
What's new

Tailstock Alignment Considerations

Kevin T

Stainless
Joined
Jan 26, 2019
Thanks to TexasGunSmith I ended up with a MT3 test bar from India. It took so long to get here that I almost forgot I ordered it! Then I found this brown sausage wrapped parcel thingy with stickers all over it on my doorstep and I was...ahhh i did order one.

So fast forward to using it. It looks the business and fits nice in my tailsotck. I lubed it with a couple drops of spindle oil. I put an indicator on it, the non taper part is 10 inches long and about .970 dia.(caliper measure for giggles) I am thinking they precision ground it from 1.00 stock. The tapered end is actually internally threaded too which seems like an extra bonus although I didn't check the threads yet.

So no matter where I am on my 6ft bed it looks lie my TS is low toward the spindle by .008 over 10 inches. So that is wear I am assuming that needs to be addressed with shimming the TS? Actually that's not entirely right. The measured dip is .010 way out in the never use area...for me! but maybe @ Raritan or Pearl Harbor she was turning some really long material?

In the middle of the bed its about .009-.008 and then near the spindle a couple thou less give or take.

I am just taking a quick test of what I am looking at to get my TS aligned with the spindle better. I have been suspect that there was an issue due to irregularities between operations but now maybe I can dial it in a little better with this tool.

So.....

What is the best course of action from here?

P10609752.jpg

P10609774.jpg

P10609796.jpg
 
So no matter where I am on my 6ft bed it looks lie my TS is low toward the spindle by .008 over 10 inches. So that is wear I am assuming that needs to be addressed with shimming the TS?

That's the well known tailstock droop. It is wear in the tailstock itself. You can line-bore the tailstock and put in a sleeve to fix the droop. Do NOT shim under the tailstock, as this isn't where the problem is. You COULD try shimming under the quill, but getting the shim to say put is a problem.

Measure again, but this time tighten the TS quill. That usually straightens up things quite a bit. If tightening things helps a lot, then don't worry about the droop. When you turn between centers, just remember to tighten your quill. If you're drilling, a drill will self-center when you start the process.

I know that it's not what you want, but many, many lathes of this era exhibit the same droop. This is one problem that is easily worked around.
 
There's more than one way to skin a cat so to speak. In that we can run a variety of checks that can confirm numbers, or show us different things. . .

First, you are low on quill end, not uncommon to wear that way. We want to straighten it up, close to, or at zero.

But second, you need to be dead center of HS spindle center.

And third, we want to see a reading from the other axis, at either 3 or 9 oclock.

Before straightening up to zero, you need to figure the second point. Where are you in relation to spindle center. One method would be to fix a dial indicator to chuck or back plate. Bring tail stock with test bar into indicator range. Then rotate chuck 360 degrees indicating off test bar, take readings. From that you can know an actual number.

Another method would be to put your new test bar in chuck (GENTLY, Not tight). center it really well, try for zero. Put a good dead center in tail stock. Bring tail stock up close to test bar. You can actually see with eye balls if you are a few .001"s off, note TS is a few high here:

464.jpg

Now you already know tail stock is pointed down, but by doing this we can tell if it is low from spindle center as well, probably. . .but we need to know. Do this check with TS quill retracted and extended.

Based on result, you can better determin if you only need to raise the quill side .009", or raise quill side .009", plus raise the entire body evenly another .005" or what ever.

In part this is why we say "Getting everything pointed at center". HS spindle, TS, and ways all in a straight line, plus to each other.

Once TS height is figured out, I would also work on the other axis. 3 or 9 oclock position. You can do this check while you are figuring out height, just to know, but I would work on the adjustment until after height is squared away. For this, test bar in TS, run the length with mag base on saddle. . . Quill retracted and extended. The dead center in TS will also help show.
 
That's the well known tailstock droop. It is wear in the tailstock itself. You can line-bore the tailstock and put in a sleeve to fix the droop. Do NOT shim under the tailstock, as this isn't where the problem is. You COULD try shimming under the quill, but getting the shim to say put is a problem.

Measure again, but this time tighten the TS quill. That usually straightens up things quite a bit. If tightening things helps a lot, then don't worry about the droop. When you turn between centers, just remember to tighten your quill. If you're drilling, a drill will self-center when you start the process.

I know that it's not what you want, but many, many lathes of this era exhibit the same droop. This is one problem that is easily worked around.

I agree you need to run checks with both TS itself and quill tight.

I don't think he's ready to shim yet, without confirming other numbers first. He has a new quill from Ted which would have tightened things up some.

But TS base, and body do split. Shimming between main body and base is a natural course whether or not base was scraped back in. Even if hand scraped in you would shim there to raise height again, because part of TS wear is its mating surface to bed.

Shimming between base and upper body to correct downward tilt is a common practice.
 
Last edited:
There are many threads on this subject in the archives. It may be worth your while to check them out. Escentially, both the spindle and the tailstock quill should be both inline and parallel to themselves and the bed. The correct sequence to check alignments is first the bed twist, then the headstock spindle, then the tailstock. The logic being that any one can influence the other measurements. In that light, you should have a spindle test bar as well. That sequence is important, otherwise, you could be chasing your tail. There always needs to be a master reference. It is always to that everything should be measured.
 
There's more than one way to skin a cat so to speak. In that we can run a variety of checks that can confirm numbers, or show us different things. . .

First, you are low on quill end, not uncommon to wear that way. We want to straighten it up, close to, or at zero.

But second, you need to be dead center of HS spindle center.

And third, we want to see a reading from the other axis, at either 3 or 9 oclock.

Before straightening up to zero, you need to figure the second point. Where are you in relation to spindle center. One method would be to fix a dial indicator to chuck or back plate. Bring tail stock with test bar into indicator range. Then rotate chuck 360 degrees indicating off test bar, take readings. From that you can know an actual number.

Another method would be to put your new test bar in chuck (GENTLY, Not tight). center it really well, try for zero. Put a good dead center in tail stock. Bring tail stock up close to test bar. You can actually see with eye balls if you are a few .001"s off, note TS is a few high here:

View attachment 304674

Now you already know tail stock is pointed down, but by doing this we can tell if it is low from spindle center as well, probably. . .but we need to know. Do this check with TS quill retracted and extended.

Based on result, you can better determin if you only need to raise the quill side .009", or raise quill side .009", plus raise the entire body evenly another .005" or what ever.

In part this is why we say "Getting everything pointed at center". HS spindle, TS, and ways all in a straight line, plus to each other.

Once TS height is figured out, I would also work on the other axis. 3 or 9 oclock position. You can do this check while you are figuring out height, just to know, but I would work on the adjustment until after height is squared away. For this, test bar in TS, run the length with mag base on saddle. . . Quill retracted and extended. The dead center in TS will also help show.


Yeah thanks I appreciate the custom note. I knew there is a lot of info on this topic but I wasn't sure if it was written for someone new to this kind of thing. I did of course run a 3 o'clock sweep and that is dead nuts! I will tinker a bit with what I am reading here and get those other threads bumped up if I can.
 
IMO...the first step is to check your tailstock without a test bar.

lock it down to the bed, extend the quill,lighty lock it, and traverse the top and sides of the quill with a carriage mounted indicator.

is also very good to turn a piece of scrap in-situ to the the exact diameter of the talistock quill as a direct comparator.

also be aware of test bar sag, its not a LOT but it will sag.
 
IMO...the first step is to check your tailstock without a test bar.

lock it down to the bed, extend the quill,lighty lock it, and traverse the top and sides of the quill with a carriage mounted indicator.

is also very good to turn a piece of scrap in-situ to the the exact diameter of the talistock quill as a direct comparator.

also be aware of test bar sag, its not a LOT but it will sag.

Thanks, I did not do this....yet!
 
also be aware of cosine error as you traverse, if you have a larger point you can use on your indicator that will help...the larger the better.

and keep in mind at the end of a ~1" diameter bar, 10" away the slightest pressure will bend it....even the spring in the indicator.

its very easy to "fix" something that isnt broken.

what you are *incredibly* likely to find is the tailsock is pointing down and away.

thats a hard condition to fix with shims, and barring rescraping the base to the bed to correct, often the best course is to kind of live with it unless its causing some real world errors.....until you can fix it for real.
 
Last edited:
Yeah thanks I appreciate the custom note. I knew there is a lot of info on this topic but I wasn't sure if it was written for someone new to this kind of thing. I did of course run a 3 o'clock sweep and that is dead nuts! I will tinker a bit with what I am reading here and get those other threads bumped up if I can.

I try to write for op, plus whoever may stumble on it later.:D

In thinking of what SLK001 mentioned about shims squirting out. . . In this case I think its less of an issue, but maybe more possible of lighter lathes, particularly lighter lathes that are engine lathes.

The 16" is pretty heavy for a "light" lathe :D. The tail stock complete is in the area of 80-100 lbs. I just stripped one down to castings, the upper casting empty is maybe 50 lbs. Atleast that's what the creeks and pops in my body were telling me. :D

Upper casting built and complete is maybe 60-70 lbs. So natural weight is going to to its job there. Part of the point is the adjusters don't pull upper body down tight to base, that upper body weight is what holds shims in place. Atleast until bed clamp is pulled tight, there's no other hardware from base to upper body.

But another point is you have a taper attachment. So you most likely won't be doing cool tricks with off-setting TS to create tapers. Once centered, it'll stay that way.

Guys with engine lathes may on occasion use adjusters to skew TS off the center line for tapers or other special cuts. That moves upper body from lower base where the shims are, side to side. If that were an issue I might special conform left and right shims as one piece each from front to rear, and might consider gluing them to base side, with oil on top shim to upper body. Or some other such means.
 
The quill is reading about 1/2 the droop over 5 inches. I did it quick as I'm a busy lad today but maybe .0045.
I have a collet closer and a shit ton of collets so that's gonna be my accuracy on the HS side.
 
You probably did this already but as no one mentioned it, have you made sure that your bed is perfectly parallel/aligned/level with itself before doing measurements?

FWIW

-Ron
 
The front face of the tailstock base wears faster than the rest.
Chips, as well as just more pressure on the front causes it.

It can be shimmed level to the bed with judicious use of the shims (more shim in the front, natch) and usually some will be needed at the back as well.

Do you have a significant wear ridge on the bottom flat of the TS base?
 
Turn down an aluminum or leaded cold roll shaft say sticking out the chuck 6" the same diameter as the tailstock test bar and butt the tailstock bar to the Head stock test bar and measure the side first and move the tailstock so the side is even on booth bars. Then make your top tests. I would move the tailstock where you use it the most and measure the top. Have you dismantled the tail stock 1/2s and checked to be sure it is clean and not burred up? When making these tests tighten the lock and be sure it is tight to the bed. Oh buy a micrometer and measure with it. The machine is old and worn, the tailstock quill and the bore it goes in is worn and until you do some measurements to assure the quill and hole are not worn you are "assuming" an issue.

To do it right you need to machine the bottom 1/2 co-planer front to back, scrape the bed and tailstock base. Then measure the test bar and scrape them to align. I bet you can't scrape? If you don't scrape you can order some "Phenolic" from McMaster Carr and epoxy the shim to the top of the bottom 1/2 even if the front shim.

All worn machines - the Tail Stock points down. I would measure the length of the bottom of the tail stock base and only measure the test bar that is the bottom length. Do you ever set the Tailstock off center to turn tapers? If you don't, slide in a shim under the tailstock 1/2's and shim it so the tailstock aligns with the turned test bar in the chuck. If you move the tails stock to turn tapers tapers then glue in the phenolic shims to make it better then it is.

Do some more tests with the turned test bar and let's see what's going on. Oh by the way I am a professional Machine Rebuilder and I do this all the time. I'm not guessing. I will also accept emails direct or you can call me. PM me and I will give you my info.
 
Turn down an aluminum or leaded cold roll shaft say sticking out the chuck 6" the same diameter as the tailstock test bar and butt the tailstock bar to the Head stock test bar and measure the side first and move the tailstock so the side is even on booth bars. Then make your top tests. I would move the tailstock where you use it the most and measure the top. Have you dismantled the tail stock 1/2s and checked to be sure it is clean and not burred up? When making these tests tighten the lock and be sure it is tight to the bed. Oh buy a micrometer and measure with it. The machine is old and worn, the tailstock quill and the bore it goes in is worn and until you do some measurements to assure the quill and hole are not worn you are "assuming" an issue.

To do it right you need to machine the bottom 1/2 co-planer front to back, scrape the bed and tailstock base. Then measure the test bar and scrape them to align. I bet you can't scrape? If you don't scrape you can order some "Phenolic" from McMaster Carr and epoxy the shim to the top of the bottom 1/2 even if the front shim.

All worn machines - the Tail Stock points down. I would measure the length of the bottom of the tail stock base and only measure the test bar that is the bottom length. Do you ever set the Tailstock off center to turn tapers? If you don't, slide in a shim under the tailstock 1/2's and shim it so the tailstock aligns with the turned test bar in the chuck. If you move the tails stock to turn tapers tapers then glue in the phenolic shims to make it better then it is.

Do some more tests with the turned test bar and let's see what's going on. Oh by the way I am a professional Machine Rebuilder and I do this all the time. I'm not guessing. I will also accept emails direct or you can call me. PM me and I will give you my info.

Thanks for the steps to move this forward! Turn a short test bar. This is in my wheelhouse!
 
Now how is he supposed to fix his tailstock without one of those starrette ultra-precison levels...

Maybe a laser too.

I am not sure if you are being facetious but I have leveled the machine and I do have a precision 12" level to get there. The mention is good medicine as was MetalCarnage Ron's above. I recently worked through a faulty back gear issue that was really vibrating the machine and have not re-checked the level!
 
The front face of the tailstock base wears faster than the rest.
Chips, as well as just more pressure on the front causes it.

It can be shimmed level to the bed with judicious use of the shims (more shim in the front, natch) and usually some will be needed at the back as well.

Do you have a significant wear ridge on the bottom flat of the TS base?

Thanks, as for the TS bottom wear, I don't recall anything that was visually surprising when I had I off the machine but I did not do any measurements.
 
I am not sure if you are being facetious ...

Yes. This is a simple lathe. If you put a centerdrill in the tailstock chuck and it does not hit center on the stock:

1) move the T/S side to side until it does.

2) put shim between the two T/S parts, until it does.

You don't need levels, indicators, micrometers or any of that, unless you plan on re-working the tailstock to make it very good, this means:

1) making a new ram
2) honing the bell-mouth in the bore
3) re-manufacturing the base to bring the height up and the low front up.
 
One simple trick is to turn a part to a point in a chuck or collet and then bring the tail center to eye-ball view a match.

Yes, this only gives the match at that one place along the bed.. *Oh I see you did that for .025 or so.
Another simple test is to set the tailstock on a surface plate to see it is flat or not flat, and if the quill is out of place/straight. .
Good to consider the tail may be wore some as well as the bed, so caution to making changes.
 
Last edited:








 
Back
Top