In article , Anthony Britt says...

In the procedures I have read previously, it is necessary to apply a
clamping load to the jaws of the chuck.

In the procedure he mentiones (which I had never
heard of before, btw) there *is* a clamping
load applied. By the jaws bearing down on the
brass stock.

It actually sounds like it might work, given that the
rod is constrainted by the two centers.

For the original poster, the reason you don't want
to use collets is that the closer will probably
interfere with the chuck's mounting on the threads
of the spindle. Depending on what taper is inside
your spindle bore, you can obtain MT adapters that
go down to the largest size dead center you have.

Use the largest diameter brass rod because the rod
will wear some as well.

The ultimate innaccuracy in your chuck is probably
due at least in part to the wear in the scroll plate
inside the chuck. Lapping the jaws will make it
center true at that one diameter that the procedure
is done at, but the wear will still be present in
the scroll so chucking other diameter stock will
still show an error - of some magnitute. I doubt
you will get a worn chuck to do better than five
thou TIR over a range of clamp diameters. If your
chuck is running out ten or twenty, then this will
make things better.

Be sure the backplate and mounting of the chuck
to same are in good order before doing any of this,
of course.

Jim

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