"David Todtman" wrote in message
news:AOg9f.361787$1i.338638@pd7tw2no...
I broke a tap today. There was not enough protruding for me to get a grip
and twist it out. I thought I would anneal the tap in situ and drill it
out. So I heated it red hot with my TIG torch and let it air cool.

When I tried to drill, I found it was still way hard and I abandoned the
idea of drilling out the broken tap. I had the flexability to drill and
tap
beside the original hole so there was really no great loss. But, what if
I
really needed that particular spot?

Would I have had better luck drilling had I cooled the part more slowly
(e.g., buried the part in a bucket of ash)?

Is my thinking nuts or is this a way to get at an offending broken tap?

TIA,
David Todtman



What was it in? If it was steel, your only choices are EDM or (maybe) a
solid carbide drill or end mill. If it was in aluminum, you can disolve it
out with nitric acid.

Jerry