How about improving your standard jaws. Many posts here about that! I hone
my hard jaws every couple of years and hols .005" which is good enough for
me. I make soft jaws for each critical job that hold .0005". I bore soft
jaws about .002" under dia of the workpiece.


"Rob Hammond" wrote in message
...

Hi folks

I'm considering machining soft jaws for a pnuematic chuck to hopefully
improve concentricity.

If I wanted to grip bars from 50mm dia to about 10mm dia would three
sets of jaws be enough? What I'm basically asking is are there any
rules-of-thumb relating bar diameter and the amount of jaw contact /
diameter?

Regards
Rob







--
Rob Hammond