Watching a demo at the county fair in Des Moines made me start quenching my small tools in used motor oil.

The smith there said it gives a more even temper on things like punches and chisels, but I'm curious if anyone else has tried this and what kind of oil they use.

3 comments

3 Comments

parker_price2mo ago

That "more even temper" line got me thinking. My buddy swears by used ATF fluid for his stuff, says it cools slower than new oil. He left a little screwdriver in a jar of it for a week as a test and the thing is still super tough. I'd be worried about the smell and the mess though, that gunk is nasty.

murphy.abby2mo ago

Oh man, the smell alone would be a deal breaker for me. I can just picture my garage smelling like a burnt transmission for a month. That screwdriver test is wild though, maybe the gunk acts like a weird coating? Still, I'd rather not have that mystery sludge all over my stuff.

smith.anna2mo ago

Honestly that whole used oil thing seems like a messy old wives tale. New oil has a known cooling rate for a reason, it's predictable. Used motor oil or ATF has all kinds of crap in it, metal bits and fuel, that can mess with the quench. Seen too many tools come out with soft spots or cracks from inconsistent junk like that. Stick with fresh quenching oil, it's just cleaner and more reliable.