Jon sez: "I want to harden a piece of steel, and from my school metal work
days,
I think that I can simply heat it to red hot and then plunge it into 'oil'."

It would appear from your question that you are using hardening and
tempering as interchangeable terms. They are not. Hardening is one
process, tempering is a different process. You can't harden just any piece
of steel. It has to have a certain minimum amount of carbon to be
hardenable. Select steel that is guaranteed heat-treatable.

Heat treating is a 2 part process. First the steel is heated and quenched -
this hardens it. However it is usually too hard and has internal stresses
from the quench. Next, the hardened steel is "tempered" which is the 2nd
process. Tempering relaxes internal stresses caused by rapid cooling of the
quench and softens the piece somewhat to the desired degree of hardness.

Select a tool steel such as O-1, (oil hardening) or W-1, (water hardening).
Oftentimes heat treating instructions are included with the steel or are in
the catalog it is selected from. Drill rod is also tool steel. Remember
there are 2 steps to heat treating steel; hardening *and* tempering.

I have had very good results (thanx to Ed Huntress and a book called "Tool
Steel Simplified") with the following:

1. Heat O-1 to red or "beyond magnetic" and quench in motor oil.

2. Then while the piece is still too hot to handle with bare hands place it
in a 375 deg. oven for 45 minutes.

I have successfully made taps and a few dies from O-1 drill rod with this
procedure.

Bob Swinney






"Jon Weaver" wrote in message
om...jon sez:
Is this the right? If so, what sort of oil should I use.. Are we
talking normal engine oil, or there there a special kind??

As you can tell, I havn't really got a clue what I am talking about,
so any info would be appreciated

Jon