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Why heat the quenchant?


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I have several knives that I am making. Two of them are to trade for large circular saw blades and three others are for a couple of guys at work that are interested in knives that they know were hand made. They will be made from circular saw steel. Most of the knives are going to be around 9" overall but one is around 16".

I am planning to quench in veg oil. I have read (I think) that I can simply quench the knives with the oil at room temp. But I have read a lot about people heating the oil to different temps. What would be the advantage of heating the oil? What kind of results can I expect if I don't heat the oil? At the present, I have no way to heat it, but I could possibly rig something up if need be.

Resident knife-maker-wannabe

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Heating the oil makes for a faster quench than with room temperature oil, as well as the oil "moves" around the hot blade when it goes into the quench. You have a propane plumber's torch right? Any metal container(pots or pans) that can take heat will be excellent for a quench tub.

Let not the swords of good and free men be reforged into plowshares, but may they rest in a place of honor; ready, well oiled and God willing unused. For if the price of peace becomes licking the boots of tyrants, then "To Arms!" I say, and may the fortunes of war smile upon patriots

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Heating the oil makes it less viscous, so it better wets the part. However, increasing the temperature also increases the length and stability of the vapor phase. FOr most cold oils, the best temperature is around 140-160F. For the vegetable oil, it really doesn't have a stable vapor phase, so you can heat it up to 250F or so without any issues.

 

Probably the biggest advantage is more uniform quench, with better distortion control - less quench cracking on quenching. If the temperature of the quench oil is too high, then properties could suffer. It depends on the alloy and the quench oil.

 

Hope that helps.

 

Scott

D. Scott MacKenzie, PhD

Heat Treating (Aluminum and Steel)

Quenching (Water, Polymer, Oil, Salt and Mar-Tempering)

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For heating my quench oil up, well I have been using it in a large coffee can for quenching smaller blades. Anyway I had this hot cut chisel I made when I started that was mild steel, I just throw it in forge and let it heat up and quench it, since it's mild it won't harden but it'll heat the oil nicely.

Beau Erwin

www.ErwinKnives.com

Custom knives

Bcarta Composites

Stabilized Woods

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Thanks for the answers. At the moment my quenchant is in a metal trash can, due to an incident that left an inch and a half gash in the bottom of my other tank. :blink: That should be easy enough to heat. But I will move to a 100# propane cylinder soon, once I get enough oil to fill it. That could be a little tricky to heat up I suppose.

Resident knife-maker-wannabe

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