Heat Treat oil Material

HI guys, I have been lurking around here for awhile reading interesting posts and gaining knowledge.

My question is, what is the "proper" type of oil for heat treating and hardening small punches and buttons and so on. I have had a machinest at work tell me "you want to use a high sulfur based oil".(

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Looking on page 493 of Machinery Handbook, 25th edition under "oil quenching baths". Various types of oils are used...... The specific heat of the oil regulates the hardness and toughness of the quenched steel.....

Doesn't sound like motor oil nor high sulphur based oil is the real answer. Then again, how critical is hardness and toughness to the overall sucess of your punches and buttons?

I "assume" it's not real critical, so the next aspect is the safety of the oil being using.

You want to use a oil that won't catch fire, and give you the approximate hardness & toughness you desire.

When it's all over and done, the best course of action might be to have it done by a commercial heat treating facility. (I worked at a small stamping plant where the owner's son experimentend with heat treating his own die parts. ONCE, resulting in cracks, etc.)

Good luck!

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High smoke point oils: I hear peanut mentioned a lot. Canola would probably work being cheaper, but cooler. Motor oil will work but might get stinky, you never know what's in there... Just remember to quench it deep under the surface so the bubbles get re-absorbed into the liquid, instead of coming to the surface and bursting into flames.

Tim (disclaimer: I've only done water quenched as yet)

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Tim Williams

At the American Bladesmith Society school in Old Washington, AR I was taught by MasterSmith's Joe Flornoy and Mike Smith to use Peanut oil heated to aprox 140 degrees for quenching blades.

For my purposes I've purchased an electric roasting pan and use it for oil quenching purposes. It will heat to 400 degrees or so, and it's plenty big enough for even large blades. You can get them at WalMart, Target or other places for between $20-40.

I documented the two week long experience at Bladesmithing school on my web site, including video and other information related to hardening if you would like to check it out:

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Good luck,


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Home heating oil is what I used to quench about 10,000 jackhammer tool steels. For small stuff a coffee can full will work well, it doesn't flare up badly if you get the tool under the surface. Control the stink by adding a little marvel mystery oil. It's best to set your coffee can inside another can you can drop a lid on. If you get good you can harden and temper in one heat by interrupting the quench but usually nobody develops that skill on one of a kind items.

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High sulfur based oil is good to use when machining, especially for threading where you don't get the oil very hot. There is no advantage to sulfur based oil when heat treating.

You can use motor oil, but if you are going to buy oil for heat treating, don't buy motor oil. Too many additives that may be bad for you when you breathe the vapors.

Some kind of vegtable oil would be better. Not as much of a polutant when it gets spilled, equally good at cooling parts at the right rate, smells much better.


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Thanks Guys for the heads up! I think that I may be visiting the grocery store for some veggy or peanut oil. I can hear it now.... Honey are you cooking fries out here??? Tracy

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Are you aware that there are actually heat treating quench oils? Look in Mcmaster car catalog.


Reply to
Chuck Sherwood

What you use for quenching depends on what you're trying to do as far as hardening. For example, some of the knifemakers use a semi-solid quench for differential hardening of their blades, the back stays soft and the edge is hard. One guy uses tallow and beeswax mixed with hydraulic fluid. It just depends on how hard you want your stuff and how fast you want it cooled down as to what oil you need to use.

When I was a starving student and didn't have a lot of options, I used used motor oil for quenching taps and dies. They worked fine for the limited jobs I needed them for. You want a high flash point and low smoke for continual useage, otherwise move your operation outside for one-offs. Quenching oil is sold by the usual industrial supply outfits, gunsmith suppliers like Brownell's and knifemaker's suppliers.


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This is correct. I use peanut or canola oil heated to about 125 for my O1 knives. You can get all fancy with various quenching mediums but the main point is to get the steel cold fast. No reason to stink up the place doing it.

Nice site. I bookmarked it for future reference.


Reply to
Frank J Warner

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