I'm currently working on a couple home-made blades and I have some questions for anybody who has heat treated O2 steel at home.
I found the following on the Hock Tools web site:
So, here are my questions:When it's hit critical temp, remove it from the heat and quickly dunk it into a sufficient quantity of oil (preheated to about 150F.) Swish it around a bit until it's cooled then let it cool to ambient in the air.
 What type of oil is best to use? I've read everything from automatic transmission fluid to peanut oil.
 My understanding is that one wants to use a lot of oil so as to reduce the chance of flash fire when the hot metal hits the oil. How do I heat up a couple gallons of oil without risking fire?