The formula is a good bit more complicated than that. Take a look at the
ECCENT.ZIP archive on my website for a program that implements the correct
formula.
Regards, Marv

Thanks, Marv. although I was not able to derive a formula - I see that I
had completely missed the bit about the width of the chuck jaws. This gets
interesting as I assume the compensation is because the jaws are no longer
tangent to the workpiece. In my case, the jaws have a slight curvature!

I will take a look at the C source code you so nicely provided and see if I
can follow the math.
thanks a lot for your work.
-- - - - - - - - - - - - - - - - -
Bill Graves RKBA!