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Paul, thanks for the information, I
appreciate, but the problem seems to come from the “spindle”
shoulder. Is this possible?
Sent: Thursday, March 31, 2005
Subject: [southbendlathe] Re: 3J
Take the back plate off the chuck and measure
the back plate only on
the machine. Make sure that there isn't a
burr or raised ding on the
back plate that's not allowing it to fully
seat against the spindle.
If the backplate is showing the run out
unfortunately you'll have to
replace it as the machined shoulder in the
plate needs to just fit
in the recess in the chuck and if you machine
it to eliminate the
run out you'll make it too far undersize.
If you have a common thread size on your
spindle you can buy back
plates with the spindle threads already cut.
However, you will need to do some final
machining on the plate to
fit it to your chuck.
Mount the plate securely on the spindle and
take a light high speed
facing cut across the entire plate to true it
to your spindle.
Then carefully turn a shoulder on the plate
to be a light press fit
in your chuck back.
Actually I guess if your current back plate
is pretty meaty you
might be able to face the current shoulder
off the plate, re-face
the plate true and turn a new shoulder on it
as described above.