Heard a guy at the hardware store say he quenches his blades in old motor oil

I was grabbing some new files in Tacoma last week and this guy was telling the clerk he uses drained 10W-30 from his truck to harden his knives. Honestly, that just sounds like a great way to get a bad temper and a lot of smoke. What's the weirdest quenching medium you've heard someone actually try?

3 comments

3 Comments

morganj811mo ago

Ever try quenching in bacon grease? That's a smoky mess that never hardens right.

mason.cole1mo ago

Smoky mess that never hardens right" sounds pretty dramatic. It's just old cooking fat, how bad could it really be? I've seen guys use worse and the steel still turned out fine. Seems like maybe the problem was the steel, not the grease.

karenhenderson1mo ago

Wait, did you just say you've seen guys use worse than old cooking fat? What on earth were they using, motor oil? That stuff is not made for heat treating metal. Bacon grease is full of salt and water, it's going to sputter and smoke like crazy. The wrong quenchant absolutely can ruin good steel by not cooling it fast enough. Sounds like you got lucky with whatever you were doing.