Tailstock alignment

[kenrinc]

I've been going through my old Logan 10" and adjusting everything to get it as straight as I can. I just noticed that my tailstock seems to be both cockeyed and high at the same time (oh, don't run with that :-)

When I bring the tailstock up to the center in the headstock it's obvious that the tailstock is higher. I think it's about .006" high since an axial measurement with a DTI shows .012 at 12 oclock.

With a zeroed DTI mounted to the carriage and run along the sides of the Tailstock barrel from front to back, I get .0015 at the back. So I think it's pointing toward the front of the lathe. Axial measurements with the DTI in the chuck are all over the map. Not sure how to interpret that yet. I've checked the ways for burrs and the obvious issues there with nothing that I can see.

Maybe the tailstock came from another lathe, I'm not sure but what are my options?

Thanks

Ken-

[SGW]

High/low alignment is of much less concern than errors in front/back alignment. With front/back, any error relates directly to the depth of cut. With high/low, the error is only as much error as is introduced by the cutting tool being slightly higher or lower as the cut progresses along the work.

The fact that the tailstock is not aligned axially with the spindle is another problem, which probably ought to get fixed so drills go straight.

[Carl]

The true test of a lathe is whether or not you can get it to turn a perfect cylinder. You can do various tests until you're blue in the face, but until you actually turn a test piece and measure it you're probably just wasting your time. Turn a test bar between centers and adjust the tailstock set-over until it is turning straight. As SGW said, the vertical off set probably wont affect it much. Try it and let us know how you come out.

[.RC.]

You could also use the search function of this forum...This subject has been covered in detail many times.

[beckley23]

There are 4 tests for the tailstock. The 1st 2 with the ram extended is to indicate the ram, vertically and horizontally, the 2nd 2 are the same except that a test bar is placed in the taper and the bar is indicated in both planes. All tests are done with the indicator mounted on the carriage.
One complicating factor is the fit of the ram in its bore. There should be no noticable shake in any direction with it clamped and a barely perceptible amount unclamped, just enough to facilitate movement.
I would also check to see if there is dirt, chips or shims between the tailstock top and the tailstock bottom.
The above tests, 10, 11, 12, & 13, are shown on p.18, Sep/Oct '04 HSM, "Reconditioning a Lathe- Revisited".
Harry

[kenrinc]

Yeah I'm pretty familiar with the search function but searching for "tailstock too high" didn't bring anything useful nor did tailstock alignment where again, too low is the rule. Problem is drilling with the tailstock chuck.

Ken-

[speedy]

Have you checked to see if the t/stock has been shimmed previously? Have you DTI'd it with the DTI attached to the cross slide and measuring the spindle height front and back??
If that all checks out...I'm not familiar with the Logan but can you shim up the h/stock to bring it into alignment with the tailstock? if not I would think that you will have to remove some material from the t/stock base.
Is your t/stock barrel or t/stock worn? When you clamp the barrel perhaps it is screwing slightly as 1.5 thou is begger all and I would suspect wear. Drilling aint that accurate at the best of times anyhow
Anyway set up a test piece and go for it cause it is an older machine and wear is everywhere man ( said the hippy )

cheers , Ken

PS- look up tailstock as the subject only, there is plenty there.

[This message has been edited by speedy (edited 04-15-2005).]

[wierdscience]

Maybe check the obvious and see if there are chips stuck in between the TS halves or bottom.

[Carl]

<font face="Verdana, Arial" size="2">Problem is drilling with the tailstock chuck.</font>

I don't think drilling with the tailstock can be considered an extremely accurate operation anyway. Too many variables, like, quality and condition of the drill chuck, length, quality, and condition of the drill bit, proper facing of the material to be drilled, and proper starting of the drill into the work. Boring is the only way to achieve real accuracy. Maybe someone else on the forum has some ideas about what to do for holes that are to small to be bored, although if you run the bit in and out enough times until it quits cutting (assuming it isn't deflecting) you will have bored the hole anyway, it will just be bigger in diameter than you intended.


[This message has been edited by Carl (edited 04-16-2005).]