Re: 3J Chuck Wobble


Paul, thanks for the information, I appreciate, but the problem seems to come from the “spindle” shoulder. Is this possible?




From: CalBoy101 [mailto:pt@...]
Sent: Thursday, March 31, 2005 1:24 PM
To: southbendlathe@...
Subject: [southbendlathe] Re: 3J Chuck Wobble


  • 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.

    Good luck-

    Paul T.

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