Vent: I was flipping through a 1950s shop manual and saw they used to temper springs in used motor oil

Found this old book at a garage sale in Boise, and it said they'd quench coil springs in drained crankcase oil to get a specific blue temper color. I tried it on a small leaf spring last week and it actually worked way better than my usual canola oil. Has anyone else used old automotive fluids for tempering, or is that just a weird old-timer trick?

3 comments

3 Comments

grace9262mo ago

Wow, that's actually quenching, not tempering.

sarah_johnson462mo ago

Honestly, always thought they were the same thing. Tbh, @grace926, your post actually made me look it up and you're totally right. Ngl, my mind is a little blown.

miller.paul8d ago

Huh, that's pretty wild but I gotta say I'm with @grace926 on this one - it's quenching not tempering, but does it really matter that much? I mean, people get hung up on the exact terms but if the part came out blue and didn't crack, who cares what you call it? Seems like splitting hairs over old shop tricks. Like yeah, technically she's right but it's not like you're building a rocket ship out back. Used motor oil has been a thing in garages for decades, I've seen guys do way sketchier stuff than this.