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Tried quenching a leaf spring in used motor oil for the first time
It came out way harder than I expected, almost brittle. Anyone know the best way to temper something that got too hard?
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the_sean7h ago
Yeah @wood.uma is right, but watch for smoke points with different oils too.
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simon_carr7h ago
Yeah, smoke points are huge. If your oil starts smoking, it's breaking down and can leave a weird taste or even harmful stuff on the blade. For high heat like tempering, something like avocado oil is solid because it has a high smoke point. But for lower temp work, a basic vegetable oil is fine. Just gotta match the oil to the job.
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wood.uma9h ago
Oh man, that's a classic first-time mistake (we've all been there). Used oil can cool things crazy fast, which gets you that glass-like hardness. For tempering, you'll want to slowly heat it up in an oven, maybe around 400-450 degrees Fahrenheit for a couple hours, and let it cool down slowly. That should bring back some toughness so it isn't so brittle.
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