What is it called and where can I get one?

rbrandes · Oct 19, 2015

I should know this, but old age must be setting in!
I need a precision cylinder with a center in each end so I can adjust my tailstock, among other things.
What is this device called and where can I get one?
Thanks in advance.
Regards, Ray

metalmaster10 · Oct 19, 2015

Most guys put a bar in and turn its OD, then measure and adjust the tailstock based on any taper witnessed. Turn again to verify adjustment.

Richard King · Oct 19, 2015

That's called a "test bar". LATHE ALIGNMENT TEST BAR 4MT HIGH PRECISION GROUND BAR - LPR Toolmakers

Found this one on Ebay. http://www.ebay.com/itm/27-Tailstoc...364700?hash=item3d0572099c:g:4IQAAOSwqu9VJWT0

You may want to call around to some used machinery dealers who sell gear machines and get a used one cheap. They are (were) common accessories to gear testers before they became obsolete and many dealers scrap the testers and keep the bars. Be sure to ask for precision ground.

Also there is a real simple method to align your tailstock. Mike the taistock quill (barrel) and turn down a spud in the chuck to that exact size of the quill, mount a mag base on compound and move carriage from your turned part to the locked up tailstock. Rich

Trboatworks · Oct 19, 2015

Richard King said:
Also there is a real simple method to align your tailstock. Mike the taistock quill (barrel) and turn down a spud in the chuck to that exact size of the quill, mount a mag base on compound and move carriage from your turned part to the locked up tailstock. Rich

Richard- wouldn't that method be off by bed wear??
That is the two cylinders would be aligned only at that specific spot on bed?

Or is this a given for worn lathe- alignment is just best effort given position/degree of wear to tailstock ways/bed etc?

Richard King · Oct 19, 2015

It references the bed saddle ways to the tail-stock ways. Plus the center line of the Head and Tail stock. One can unlock the TS and move it down the bed and lock it and test it at different locations. I've been doing it this way for 40 years and it works 99.9% of the time. I have seen 1 or 2 crap import machines where the ID and OD of the quill bore are not the same, but on good Iron this works good and no need to buy a test bar. If the bed is worn you will get error on a precision test bar too, or turned test bar and all you can do is get it as close as you can. Rich

Trboatworks · Oct 19, 2015

OK- thanks.

I will have to try on my old lathe which has both bed and tailstock way wear.

rbrandes · Oct 19, 2015

Richard King said:
turn down a spud in the chuck to that exact size of the quill, mount a mag base on compound and move carriage from your turned part to the locked up tailstock. Rich

Rich,
Thanks for the education. I think I will try your method.
Regards, Ray

Pete F · Oct 19, 2015

I agree with Richard, a test bar just to align a tailstock to centre is way overkill.

The spud method is a good one. Otherwise just chuck and turn a live centre and throw a piece of centred stock between centres. Clock the headstock end and mark the bar where you've clocked it. Remove the bar, flip it end for end and clock it at the tailstock end until it reads the same as the headstock. Unless the tailstock was waaaay off to begin with you should be able to get it right on the first iteration and it will measure the error at the actual centre.

Zahnrad Kopf · Oct 19, 2015

Pete F said:
I agree with Richard, a test bar just to align a tailstock to centre is way overkill.

Maybe. But I've got a few laying about for other duties and they work very well for the purpose, quickly. Ray, if you decide you just have to have one, I have extras that I do not use and could sell or barter.

Milacron · Oct 19, 2015

Closed due to meaningless topic title

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