From: rhock@mcn.org (Ron Hock)
Newsgroups: rec.crafts.metalworking
Subject: Re: Heat treating steel
Date: 21 May 1996 15:50:42 GMT

>To judge "cherry red" on drill rod, I heat until it becomes non-magnetic, 
>then get it a "tad" hotter.  The trick part is holding this temperature 
>for at least 5 minutes (for small pieces); 20 minutes is better..

The amount of time required at critical temp (1450-1500F for O-1)
depends on the thickness of the stock. Since the carbon is "as if in
solution" at the critical temp, it can and will migrate to the surface
and be seduced away by all those fast and loose oxygen sluts.
Therefore, we want to hold the metal at that temp no longer than needed
to ensure the transformation to austenite, loosing as little carbon as
possible. 

In my experience, once the steel ceases to be magnetic, it's ready. Do
allow it to go slightly above that temp to be sure that you have enough
time to reach the quench tank before it drops below critical.

>I think the crayons work better in an oven (which I don't have, either.)

I tried the crayons, too. I hated them for the same reason you do and
never used them again. If you're tempering in the kitchen oven, you can
use a little pile of the crayon crumbs as an indicator for the low-temp
draw. With O-1 for Rc62, go to 325F.  Of course, you'll need a 325F
crayon...  Good luck.

Ron Hock (rhock@mcn.org)
Hock Handmade Knives
http://www.mcn.org/a/rhock/hockhome.htm