Tailstock height adjustment, Logan 12x36

[Long Tom]

I have a fairly beat Logan 2557 VH. Got it late last year and had to put it to work right away, which was fine as most of the parts I made were close to the chuck and involved working on all surfaces, so the overall alignment of things wasn't crucial.

In the fullness of time I'm intending to make this machine all it can be. New chuck, centers, tailstock chuck, belts, and so on. TIR at the spindle is minute- maybe a tenth- certainly smaller than I can measure reliably. However I recently had to make a long mandrel and, of course, was cutting a bit of a taper. So with a lull in the action I'm fixing that.

I've got the tailstock aligned side to side (90 degrees to the ways), but I'm showing it to be a couple thou HIGH. I'm indicating off of the Morse taper in the tailstock, using an indicator set off center in a triangle of wood in the chuck... sort of the Tubalcain method.

The tailstock was shimmed in the past with two layers of brass shim stock. It appears that one layer is 3-5 thou thick and the other 1-2 thou thick. I've only got dirty, ragged edges to measure so it's tough to know exactly until I take it apart.

I was gonna crack it open and remove the thinner shim, but even though its contrary to my nature, I'm learning that it's best to slow-play things of this nature rather than plunge in. To that end the tailstock has been sitting in my workbench the last couple of days as I think about it. In that time, it occurs to me that I didn't clean the taper opening before I measured, and, the unit may have been shimmed so that it was "on" with the tailstock spindle run out a few inches and drooping a bit. So, I'm going to remount the thing and measure again.

Your thoughts appreciated. I'm a little mystified as to WHY there'd be the need for that much shimming in the first place. The ways are quite banged up near the chuck- perhaps it was a student lathe and got it's tailstock switched with another Logan?

Also, does the tailstock come apart just with the two side-side adjustment bolts?

[GlennW]

I'm not real clear on your method, but be careful as indicators can play tricks on you when inverted!

Flat, note my feet.



Horizontal



Inverted



In your application, the indicator would show the tailstock bore being high.

One way to check would be to start with the indicator facing up and the contact point touching the lower surface of the bore. Note the reading, and then do it again starting with the indicator point contacting the upper surface. If it is "indicator sag" the readings will differ.

[coal miner]

That's eye opener !

[GlennW]

It's all about the mount and setup. That is a very short, rigid Noga arm.

Here is the same test using just the indicator held firmly to a block.







The indicator itself is usually not the problem, but can be.

[Long Tom]

I'm using a plunge indicator and coming into the tailstock taper mouth at an angle. I don't *think* droop could be an issue. I'll give that some thought. I'll snap I pix of my hillbilly way of doing it and post it up for the sake of amusement.

[dly31]

There is certainly nothing wrong with trying to get everything as well aligned as possible but I can't think of any reason why a 0.002" high tailstock would cause any detectable error in a machined part. Also you would need to know if that error was constant with extension of the ram and movement of the tailstock along the ways before deciding on a correction method.

[Russ Hanscom]

Tail stocks frequently come a few thousandths high from the factory, to allow for future wear. If you have the tailstock set correctly laterally, that difference in height will not cut a measurable taper under most conditions.

[refinery mike]

Russ is right that is a normal situation do not do anything. that one got me too, an old machinist explained it to me.

[Patio]

I'm using a plunge indicator and coming into the tailstock taper mouth at an angle. I don't *think* droop could be an issue. I'll give that some thought. I'll snap I pix of my hillbilly way of doing it and post it up for the sake of amusement.

Without seeing the set up, my comments may not be correct. But I would wonder how well you could get a reading in a bore, with a plunge indicator, and if you are measuring with a plunge indicator at an angle, I would think the readings would not be correct, without some math and knowing of angles involved.

Then there is the, why is it shimmed in the first place? You did mention that it may have come from another lathe. If that were true, then it would have to have been fit, to that lathe, to run true.

Just my thoughts, but I am a new guy too.

[Harold_V]

I'm using a plunge indicator and coming into the tailstock taper mouth at an angle. I don't *think* droop could be an issue. I'll give that some thought. I'll snap I pix of my hillbilly way of doing it and post it up for the sake of amusement.

You don't *think* it can be an issue?

You're in for an education, especially because it's a plunge indicator. More weight, and indirect readings. Not a good setup at all, even if you can eliminate sag.

A tough lesson to learn is measurements that are not factual are also useless.

Anyone can guess.

It's the guy that can prove a reading that has a chance of achieving the proper goals.

Harold

[Richard_W]

I've got the tailstock aligned side to side (90 degrees to the ways), but I'm showing it to be a couple thou HIGH. I'm indicating off of the Morse taper in the tailstock, using an indicator set off center in a triangle of wood in the chuck... sort of the Tubalcain method.

I wouldn't worry about a couple of thou high as others have said. I do wonder however about indicating in the bore? Has a taper shank drill been spun in there damaging the bore? If so it may not be the best way to dial it in. I dial around the outside of the spindle with it extended and locked. Then check it in two places and see what it looks like. Often it goes down or up hill on worn machines. The reason I lock the spindle is it removes the wear by pushing the barrel tight against one side in the bore. The lock on some lathes lift the spindle and some push it down. So locked would be the position you would turn between centers.

The tailstock was shimmed in the past with two layers of brass shim stock. It appears that one layer is 3-5 thou thick and the other 1-2 thou thick. I've only got dirty, ragged edges to measure so it's tough to know exactly until I take it apart.

The wear from sliding the tail stock back and forth may not be and often is the case worn tapered. So the spindle is pointing gradually up or down based on how it worn to the ways. Often times the under side of the tail stock is worn in a bannana shape where it rocks and doesn't make full contact with the ways. I have had to put shims in a 17" lathe because the tail stock was low but also pointed down toward the head stock. This required 4 stacks of shims that progressively got smaller toward the right end of the lathe. Since the company didn't want to fix it right even though they had spent the money to have the ways plained and scrapped in. This made the spindle level and on center when clamped down. This made it so you didn't have to compensate for taper everytime you turned a shaft of a different length. While it wasn't the perfect solution it made the lathe easier to use. I guess what I am saying is the shims may not equal the same thickness all the way across the length of the tail stock. Unless the tail stock had been scraped in and the split on the lower half remachined to be parallel to the center line.

Hopefully not much of this applies in your situation.

Richard W.

[Long Tom]

I'm using a plunge indicator and coming into the tailstock taper mouth at an angle. I don't *think* droop could be an issue. I'll give that some thought. I'll snap I pix of my hillbilly way of doing it and post it up for the sake of amusement.

You don't *think* it can be an issue?

You're in for an education, especially because it's a plunge indicator. More weight, and indirect readings. Not a good setup at all, even if you can eliminate sag.

A tough lesson to learn is measurements that are not factual are also useless.

Anyone can guess.

It's the guy that can prove a reading that has a chance of achieving the proper goals.

Harold

Thanks Harold.

You are, of course, correct. I've been taking this slowly because I'm painfully aware that I'm a babe in the woods here to some extent.

I don't think the indicator tip is drooping. On the other hand it's possible my whole dang setup is drooping!

The other way I've tried to measure this is with a co-ax in a collet. However, I don't have a proper collet closer and that makes that suspect. I'm going to put the tailstock back on the lathe and see if there's agreement between the two methods, and also test the repeatability of my method with the plunge indicator.