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Tried quenching a leaf spring in used motor oil and it didn't go how I planned
I had this old leaf spring from a truck and wanted to make a knife. My buddy said to quench it in used motor oil instead of new, said it would be slower and less likely to crack. So I heated it up to non-magnetic, got it in the oil, and it just didn't get as hard as I expected. The file still bit into it pretty easy after. I think the oil was too dirty and maybe too cool, like 80 degrees. Learned that the condition of your quenchant matters a ton, not just what it is. Has anyone else had weird results with different batches of used oil?
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blakem376mo ago
Thought used oil was always better too. Your post changed my mind.
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rubyk866mo ago
Did your buddy at least tell you what kind of motor oil it was? Some of those modern low-viscosity synthetics are basically fancy water and don't quench for crap, even when they're new. A lot of the old advice assumed you were using thick conventional oil.
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adamgreen6mo ago
Tell me about it, I tried quenching some 5160 in a bucket of old ATF that had been sitting in my garage for a year. It was basically full of water and rust flakes, and the piece came out softer than when it went in, lol. @quinnr40 is right, that advice was a total dipstick move. You really need to know the history of your used oil, because one batch can be fine and the next is just sludge that won't pull heat fast enough. My lesson was that free quenchant is only a good deal if it actually works.
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