On Thu, 7 Jan 2010 05:40:24 -0800 (PST), Jim Wilkins
wrote:

On Jan 6, 11:30*pm, "Martin H. Eastburn"
wrote:
...

If you take a machine and add higher precision/accuracy to it the worst you
get is the machine spec. *If you add lower quality parts, the machine degrades
to the precision/accuracy equal to the worse values.

Martin

Unless you can use the machine tool to custom-fit the part, like a
chuck backplate.

And that's what I'd suggest Iggy do, at least until he sees how often
he really needs a center in the headstock. In the meantime, make a
mild steel center that fits directly in the spndle. The taper can be
picked up by sweeping the spinble bore with an indicator and the
compound. Tweak the compound after checking the fit 'til the tapers
match. True up the point on the center each time you install it in the
headstock and it'll be at least as accurate, and probably better, than
a purchased adapter and center.

--
Ned Simmons