Milling Vise Fixed Jaw - How Flat Should It Be?

[Phil3]

My small milling machine vise (3") fixed jaw appears to be out .003" or a bit more when measured with a test indicator across its face. It took a heavy hit on the back left corner of the jaw (good 1.25" or more from the jaw face), making me wonder if I tweaked the vise. But I don't know if .003" is normal or not. The indicator stays still as I crank the mill table along the X axis, until about the last 30% of the vise jaw face, on the side where the impact happened.

Phil

 

[Tony Wells]

Ideally, vise jaws are hardened and ground, and should be close to zero when indicated in. In -Z-, there could be debris under the vise that elevates one end or the other.. If there has been a wreck,remove the fixed jaw if possible and lap it back flat if there are any lumps.. If you have a surface grinder, so much the better. Regrind both jaws on the grip face and mounting faces, then mount them back in the vise for dressing the other three surfaces. Assuming the bottom of the vise is flat, this should put everything back in place.

0.003 out of straight is too much.