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.

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

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

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

Model Engineers Workshop issue 290.

Readallabouddit.