Well, in the first place, 440-C isn't really stainless steel. Stainless steel is what we make pots and pans, flat wear from.
440-C is a stain resisting Hi-Carbon steel. They are probably somewhat correct. It is that we just aren't using what they are talking about. Average machine shops have no experience with what we are using, Much less for our intender purpose.
The books say 1 hr at temp for ever inch of thickness. None of us are making 1" thick knives! Aha!
Wrap in a good stainless foil. (available from just about any Knife Supply House.
There are many methods. But 15 minutes is just about max at temp for a typical hunting blade in 440-C. There is no reason to hold it longer and loose much of the carbon you bought it for in the first place.
After a strong air quench, (4 bar, or min of 56 lbs,) of moving air, or plate quench, place in over (while still warm, to the tempering temp you select for the desired results) Hold for 1 hrs. Most stop there. I go for two hours there times.
If you don't have shop air, quench in a very strong air current of fan air. The colder the better. Placing between two plates of thick alu. also works well. I use a combination of plates and forced air.
Mike
