Might want to check this out:
http://www.americanbladesmith.com/ipboard/index.php?/topic/419-discussion-on-quenching-techniques/?s=a6cca3e140d9792ede124e9950412ce3
ok so to sum it up my quenching technique is kinda squirly lol. ill work on a more consistiant quench. what oils are good to use, other than used motor oil?
I know of guys getting good results with canola, peanut, and vet grade mineral oil. That being said, it also depends upon what steel you're using and what you're wanting to do with it. Kinda goes to that thought of it might work, but am I getting the best results? If you're the hobbyist making knives for your friends and you, probably no worries. M.S. Ed Caffrey used vet grade mineral oil up through his M.S. test knives which clearly did well for him. But, he did a lot of work to know his process well and to be very consistent to get consistent results. He now uses some of the manufactured quenchants and I think high temp salt tanks, too.
M.S. Cashen has said a few times over that taking the guess work out of what quenchant is being used is a big deal. If something isn't going right, you can in theory begin looking at everything BUT the quenchant, because they are made specifically for it and to certain standards. I'm looking at getting some Parks 50 because I want the maximum martensite and as good a hamon as possible from steels like 1095 and W1 and W2 when I start using it.
Sorry if that was too rambling, but wanted to give you some of what others have been kind enough to share with me. I'm sure others that are smarter than me will add to or correct any flaws mentioned above.
Jeremy
Kevin Cashen lives not too far from me and I've bought a couple of pieces of his O-1/L6 damascus. I've seen him heat treating using his salt tanks and this man is an artist with the heat treats. He can make a piece of O-1 perform like some kind of super steel with the careful control he has over the process.