I think you are right to be cautious about putting the jaws to a grinding wheel, but a light "stoning" by hand might remove possible burrs on the gripping face of the jaws.

Apart from this, a supply of small brass packing pieces is useful but a difficulty with using these is that they fall out very readily whilst adjusting the chuck one jaw at a time. An improvement is to make a second chuck-key so 2 opposite jaws can be moved together thus avoiding the packing falling out. This also greatly speeds up centering of the work. This key doesn't have to be very robust.

BTW, soft jaws are usually for self-centering scroll chucks.

Edited By Clive Brown 1 on 29/04/2020 20:57:27

The jaws were probably ground with a very small wheel, which results in the sharp edges touching first on anything of larger diameter than the grinding wheel. Assuming the four jaw is independent, removing the edges would not be likely to spoil tis accuracy. I would put a sheet of 1000 paper on a flat surface with a square sided block on it. Then I would give each jaw in turn one light stroke longitudinally resting against the block. Try to make each stroke of each jaw as equal as possible, using a fresh part of the paper for each. Wash the jaws before re fitting them. It would be a good idea to keep each jaw in its original slot. This might be too slight to notice any improvement, but better safe than sorry.

Bob,

I have in the past wound a couple of turns of masking tape round the workpiece to soften the bite. Like you, I have all sorts of odd ends of split copper pipe but these tend to get mangled and bent after being pushed over different sizes of job.

I agree with Clive Brown and endorse some light stoning on the jaws, especially the edges.

Regards Brian

How about a collet chuck? …or turn between centers with a drive dog?

Ed.