On Wed, 16 Jul 2008 08:04:01 -0700 (PDT), Gerry
wrote:

Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage
Greetings Gerry,
Consider just the chuck itself and not how it mounts to the spindle.
Inside is a scroll plate which is centrally located by its bore. This
bore must be a close fit on the register in the chuck body itself in
order for the chuck to repeat. The jaws are located by the scroll.
This means that the scroll, which is a spiral, must be machined
accurately and on center with the bore in the scroll plate in order
for the chuck as a whole to repeat. If the jaws and their associated
scroll sectors are machined accurately then they should repeatedly
chuck parts on center. When the chuck is tightened the scroll plate
is subjected to offcenter loading which will tend to push it against
the side of the bore in the scroll plate. If the bore isn't a close
fit the scroll will shift off center. So hammering on the jaws may be
shifting the scroll back to center. It's also possible that there is
dirt in the scroll and chuck body that is shifting around. Your best
bet is to take apart the thing, clean all parts well, and measure the
clearances. Then you can determine what is really going on. Think
about this: it's possible that if hammering on the jaws brings the
part on center then cutting forces may push the part off center. Then
it will be really hard to decide what exactly is happening.
Eric