Beginner's guide to tailstock alignment

Having noticed a tapping hole I drilled for an M5 thread on my Myford ML7 was a bit oversize when I ran the tap down it, I remembered the tail stock alignment article by Pete Barker.

I followed Pete's instructions and cut a test bar between centres and measured the bar each each end. It took me seven goes but I finally recorded an error of 0.000,05" on my Kennedy micrometer which is the limit of its accuracy. Feeling well chuffed with myself, thank you Pete!

I probably could have got pretty close with fewer cuts if I had been more observant and noticed that one of my cuts was too shallow and did not cut the full length of the bar thus giving me a false reading. So not that smart after all...

Graham S

Well done. Glad the article was of help to you. Its very satisfying how accurate these old lathes can be with a bit of careful setting up.

Pete

It's sometimes a good start simply to set a centre in the tailstock, turn a 60 degree cone in the chuck, bring up the tailstock to meet, lock its slide and quill, then look at how the 2 points align under the best magnification you have.

0.000.05" Are you sure ?

The second point is probably a typo. That is assuming the mic is digital, 0.001mm or 0.00005"

A quick method of aligning the tailstock for general work is to bring the headstock and tailstock centres together and hold a steel rule between the tips. Then adjust until the rule is square to the lathe axis.

Machining a dumbell type test bar and measuring both ends until they are exactly the same diamerter (within a fraction of a thou with a micrometer) is the best method. No machining is required if an existing test bar is used with a dial indicator on the carriage. Measure at the headstock and move the indicator to the opposite end without adjusting the cross slide and adjust the tailstock until they read the same.

Any bar with centres on both ends and only one accurately turned end can also be used. Put the bar between centres and measure with the dial indicator at the headstock end. Remove the bar and move the indicator to the other end then turn the bar end for end between centres and measure again. (similar to useing a test bar and the reference diameter is exactly the same).

Paul

Or roughly the change in diameter of a one-inch bar for a 3-deg C temperature change.

Edited By Bandersnatch on 03/03/2020 01:37:55

Where is said article please? I would like to have a read Ta

As a service engineer in regard to the tailstock alignment problems I would always mount a DTI in the headstock chuck and rotate the chuck with the finger checking the inside of the taper looking for out of alignment both up down and front to back. Then repeat this with the tailstock clamp so see if the clamp significantly pushes over the tailstock spindle when clamped. (You can turn between centers with it locked but you can't drill etc with it locked) I would then use an extension bar about a foot long in the chuck and repeat the the process. The other check would be to put a standard Morse taper bar in to the tailstock and using a DTI clock the length of the bar over the top and along the side. Only after this was done would I do any adjustment to rectify the possible faults like droop, crabing, or other wear problems. Putting a bar between centers and adjusting till you get a parallel bar is good for a specific job but if there is other problems when you change the lengths you may be out of speck. The most problematic thinks were wear in the tailstock bore, wear on the base of the tailstock causing droop and damage to the taper inside the spindle.

David

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There is a big clue in the subtitle of this thread

MichaelG.

Model Engineers Workshop issue 290.

Readallabouddit.

Ahhhh, that would explain why I hadn't noticed it! I have a friend who subscribes to that. Cheers

Yes, I was only aiming for an error of less than a thou' but got a reading of 0.000,05" just by luck.

As a matter of interest are my commas showing on other peoples computers as full stops?

Your commas are showing as commas, just people can't read or type what you wrote.

Edited By JasonB on 03/03/2020 13:08:45