Oil Quenchant for Heat Treating

[Bob H.]

Actually, used motor oil can carry a wide variety of contaminants. Some very nasty stuff can be in there, that you do not want to breath. I currently use new ATF fluid, but will go to Sams Club and buy the soybean oil they have, same as Ellen has suggested in the past. Something like 5 gallons, for a very low price.

Bob Harasim
Coyote Forge

[Tyler Murch]

Originally Posted by Nolano

Tyler, Ive never found automotive oil to be a "too slow quench", I've made plenty of tools with it. At my local Costco(Huge warehouse store that sells in bulk) I remember you could be an extremely large bottle of soybean oil(I'd guess 2-4 gallons, it only measured it in pounds, strangely) for $13.

Maybe you are quenching at too high a temperature.

[Nolano]

Hmm, its working fine for me, so I must be doing it wrong. Of course!

But yeah, I am going to get a few gallons of veggie oil soon.

[Tyler Murch]

Notice I said BURNT motor oil. Not sure about new stuff

[Nolano]

Ah yes, well, this stuff is not burnt, merely old stuff that has been changed out after its recommended service life.

[ApprenticeMan]

I have an oil quenching question. Say with water and a 5160 knife blade, you heat it up to critical/non magnetic and quench it(hardening?), then temper, right? But with oil, because it is not such a quick rate of cooling, woiuld a knife blade still need to be tempered, or could it just be hardened in the oil and be usable and tough?

[Mills]

What is "burnt" motor oil?

[sandpile]

A.M. carbon steels irregardless of quenchant have to be drawn back to the hardness you want. If left completely hard, they will break like glass went dropped.

Chuck

P.S- Don't put 5160 in water for a quenchant.Grin.

[Ellen]

35# of new soybean oil at Sam's Club for $13. That's about 5 gallons. Works great, no smell, much higher flash point than most other oils. Yes, you still need to temper the blade. The kitchen oven at 350 to 400F, depending on your desired result and starting steel works great. You'll be glad it's not used cooking oil when you temper the blade inside the house. Make sure you buy the pure oil, some of the frying oils have additives in them and I am not sure how that will affect the quenching results. Use a large enough quantity of oil for the blade, stir in a figure 8 pattern, pull the blade out when is cooled to a black heat, and let it air cool, then temper it in the over. The air cool from a black heat to a "hold in your hand heat" will give you about 15 minutes of crucial time for the transformation of the martensite in the blade steel and will eliminate the need to "triple temper" the blade. I've used this technique on O-1, 1095, and 5160.

[TarAlderion]

Sandpile is right A.M. If you quench 5160 in water you will crack it, unless you are extremly lucky, but in most cases it will crack. And if it doesnt crack it will be brittle beyond any use. You must use oil.

And, if you harden a blade and it does not need tempering afterwards that means it did not harden in the first place. You must always temper or your blade will not be of any service and will break with the least amount of stress.

When I get some more $$ I might check out that soybean oil, sounds good.

Tar Alderion