"jtaylor" wrote in message
...

"Ed Huntress" wrote in message
...

If you mean that somebody got it red with a torch and then walked away
g,
that's another kettle of fish. Or another piece of wrecked steel.


I was at a shop where in the back a pair of fellows were hardening the
teeth
of a large gear. Don't know if they made it but it would make sense -
they
were a machine shop after all. The gear was about 12 inches long and
almost
the same width, teeth were about an inch and a half or so from root to
crest. One fellow had a torch and was getting each tooth red-orange,
whereupon the other would douse it with water from a garden hose.

I hope that was a case-hardened gear. Otherwise, I hope that it wasn't a
gear for a helicopter. g

There are three basic ways to harden gears (through-harden; flame-harden;
case-harden), and it's very tricky if the gear has to handle any load. It's
really easy to wreck one, especially with flame-hardening. Flame-hardening,
or localized induction-hardening, usually is done in a special fixture and
semi-automated.

--
Ed Huntress