Steve wrote:
I was reading up on lapping chuck jaws and came across the thread
about using a brass bar and valve lapping compound to do the job. I
want to make sure I understand the process before I try it.

1) Get a brass rod 18" long and 1.25" in diameter. Face and center
drill both ends.

Problem one. How do you ge the bar accurately center drilled if your
chuck is shot? I guess you can still do it with a steady rest.

2) Put a dead center in the spindle and another in the tailstock.

3) Center both ends in the dead centers and turn a section long enough
to make sure that it is perfectly parallel to where the chuck jaws
would clamp onto it.

4) Tighten the jaws onto the brass bar to where you can barely turn
the rod by hand with the rod still being held between centers.

5) Using a screwdriver paste on some 320 grit valve grinding compound.
Turn on the lathe at one of its slowest speeds and grind the jaws
until the bar loosens up on the jaws.

Yeah, this is going to be a SLOW process. You may need to cut down
..010 to .020" (.25 to .5 mm) on badly bellmouthed jaws. Mine were like
that on one old chuck. This could take DAYS with lapping compound.
If the problem is only one jaw being a little high or low, it might not
be such a big job. But, that is most likely due to chips in the
scroll, not wear.

6) Tighten the chuck jaws a little and grind again.

7) Grind until you can see grind marks all along each jaw.

Chuck up a drill blank of the same diameter you used to turn the jaws
and check for runout.

Is this correct?

Where do I get the adaptor to hold the dead center in the spindle?

Most lathes accept a dead center of the right taper directly into the
spindle. You just tap it in with a lead ball.

A far better process is to adapt a grinding tool (toolpost grinder or
Dremel, etc.) to the toolpost and grind the teeth. You can even cut
the teeth with standard boring bars.

Jon