"Rob Kramer" wrote in message
. ..
Hi all,

At a recent watchmaker's fair I bought a small vice. Old, in bad shape,
but
better than anything I've got at the moment. The thing actually cracked in
half somewhere in its lifetime and was welded back together by someone
with
a very big welding machine. The problem was that the jaws were not
parallel
properly after that; there was a .7 mm gap on one side.

I've annealed the jaws and filed and sanded them back into shape. They
close
well now, and are beautifully straight, smooth and polished, just as I
wanted.

My question: how can I best re-harden them? The jaws are only 6 cm wide,
but
I'm only used to working with tiny pieces of steel to make watch
components
or small tools. Can I just heat to cherry red and quench in oil? And then
temper by re-polishing and heating to some colour (blue, for example)?

I only have a torch, no kiln or something like that.

Cheers!

Rob


Assuming the material is medium carbon steel or better, you can heat the
jaws until they are no longer magnetic, then quench. You risk cracking
them if you quench too quickly, so oil may be the better choice. Once
quenched, do as you suggested and draw back the hardness ever so slightly.

When you quench, it's important that you insert the jaws in the quenching
medium such that one side does not cool faster than the other, otherwise
you'll bow the pieces and you'll not be any better off than you were before.
Inserting them straight in, from one end, is likely the best choice.

The best scenario, judging from your description of the repaired broken
body, would have been to make the corrections on the body of the vise
instead of the jaws, which could then remain parallel and could be easily
resurfaced without effort, using a surface grinder. Hand working the jaws
may still prove to have been a bad choice.

Even with proper quenching, you may find that the jaws don't remain flat,
and will need to be worked once again.

Luck with the project! How about a report after you've finished?

Harold