Tailstock vertical alignment???

One other check that you could make is to mount a piece of 1/2" round with about an inch sticking out of the chuck. Turn the compound around to -30 deg. and sharpen the piece. Check again with a dead center in the tailstock.

Robert D.
 
Old thread, but been thinkin' on it for awhile.

Suppose that the tailstock chuck were worn enough that loose jaws and a long/heavy drill bit would settle aimed downward, from gravity.

One way to test this would be to apply upward pressure on the drill bit tip while tightening the chuck. Then, see if its center has changed...
 
No movement under moderate pressure and a heavy drill bit installed.


I had a medical induced stand down (stitches in the hand, see safety forum) , so I've spent the last 2 days looking at this lathe. Using my best dead centers and taking my time, the tailstock center point is about 1/16" lower than the spindle center. I'm assuming wear to the bottom of the tailstock, so now I look at shims.

Do you try to shim between the tailstock and the lathe bed (how do you keep them in place, mini pins?) or between the halves of the tailstock where it slides for adjustment (looks like the retainer fingers would be a problem)...???
 
I think that you already confirmed that the ram was parallel to the bed (no droop). The shims should go between the tailstock casting and the base. So two pieces to clear the key and keyway. Bed wear due to tailstock movement is probably negligible. It doesn't run on the same part of the ways that the carriage does.
 
I had some 1" wide brass strips that came with the lathe. The thinnest was .0165" and placing a strip between the halves of the tailstock put the dead centers point to point...visually as close as I can get. I used 2 strips, one under the front and one under the back right at the front and rear edges. There is now a gap between the halves, but I don't think that will be a problem.

There was not a great deal of wear to the bed contact surface...the original machining marks are mostly still visible.
 
Now when you think that you have the problem solved, turn a test bar between centers. That is when you will find out whether you still have a problem or not.
 
The best way to check the ts quill and bore is to turn a piece of stock to the exact diameter of the ts quill. Run a di along the side of the part then on the side of the ts quill. Do the same for the top side of both. This will give all the alignment and accuracy tests for the ts. Much easier than turning two collars.
This method was shown to me by a machinery rebuild of the highest regard.
 
But how do you differentiate between misalignment from elevation and misalignment from horizontal offset? Both would show up as a diameter change between head and tail ends...and both could be larger or smaller (or offset each other). Without a properly aligned tailstock, I simply can't turn a piece and get uniform diameter the entire length!
 
Except on very small diameter parts, diameter error caused by tailstock height error is about two orders of magnitude less important that back-set error.
 
CDHKnives, I think that he means to turn a piece in the headstock chuck without it's being supported by and affected by the tailstock. If you have an extra ram, you can use that but you will need to use a 4-jaw chuck so that you can zero out the runout. With that setup, you would merely zero the dial indicator on the piece in the headstock and then run the carriage over and check the tailstock ram both fully extended and nearly retracted. And adjust as required. However, keep in mind that all methods will potentially be affected by bed wear. As I wrote last night, vertical error is less important than horizontal. See the .TXT file attached. When Downloads works again, it will be in there.
 

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  • Tailstock Height and Bed Wear Errors.txt
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