Check the jaws and the face of the chuck for where the problem is happening.
Odds are that the jaws have a rough finish inside the grooves for the face
or the face has a rough cut on the slot. Look for bright spots that have
formed from the upsetting of the metal and file them (not the whole area but
just the little bit of bright spot) down a little and try again. Make sure
that you get the jaws go into the correct slots each time or you may end up
with problems.

--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!