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Spent 3 years quenching in dirty water until a cracked blade taught me better
I had this old 55 gallon drum I used for quench oil and never changed it out. Figured oil is oil, right? Last month I was heat treating a chef's knife and it came out with a hairline crack right down the middle. An old timer at the local blacksmith guild meeting took one look at my setup and said "when's the last time you filtered that sludge?". Turns out all that scale and crud building up in the oil messes with the cooling rate. I swapped to fresh canola oil and my last three blades came out perfect. Anybody else ever mess this up for years without realizing it?
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victorhill13d ago
Wait, is dirty quench oil really that big of a deal? I've been using the same bucket of motor oil for like five years and haven't had a cracked blade yet. Maybe you just got a bad batch of steel or something.
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Oh man, this hits way too close to home. I had the exact same problem with my quench oil for like two years. I was using this old motor oil I got from a buddy and just kept adding more when it got low. Never even thought about all the little bits of scale and dust settling in there. Then I did a batch of hunting knives and three out of five warped like bananas. Switched to fresh canola and filtered it through a coffee filter after each use and everything's been solid ever since. It's amazing how much junk we overlook just because it was working good enough.
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