The message . com
from contains these words:

I hope someone can tell us how to either remove the
gripping pieces inside the assembly or where I might get another chuck
assembly please. The action and the condition otherwise are great,
worth fixing,

As far as I remember they just unscrew.

http://diytools.com/product/52500.htm

might help.

--
Skipweasel
Pay no attention to that man behind the curtain.