Doug Warner wrote:

Myford ML7, small 3-jaw chuck. No matter how tight I crank down on
it, pushing sideways on the end of a 8" bar will cause the bar to
shift, and the end to run untrue. Merely loosening and retightening
it will lose centering, at least at the far end.

Repairable, or do I have to buy a new chuck?

It's not the spindle bearing, since I don't see the same problem with
a smaller bar in a collet.

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Use an indicator on the chuck body and each of the chuck jaws while you
try that push test. If they move, then either the chuck body isn't
seating right on the spindle or the jaws and their slots are well worn,
and you'd be better off replacing that chuck.

If the chuck and jaws stay put, then you probably need to true up the
contacting surfaces of the jaws, because they've probably become curved
through wear.

If you search around you'll find references on how to do that, including
how to support the jaws during the operation. You can dress them with a
Dremel tool with a rotary stone in it clamped to the toolpost, while the
chuck is rotating at a slow speed. That's what I've done more than once.

Jeff


--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone
to place the blame on."