Spent 4 hours trying to get a good heat treat on a piece of coil spring

I was working with an old leaf spring from a pickup and couldn't figure out why it kept cracking. Turns out I was quenching it in the wrong oil, took me three ruined pieces to realize my canola oil was too thin. Anyone else have a specific oil that worked better for 5160 steel?

2 comments

2 Comments

gavine411mo ago

. Oh yeah, the canola oil from the kitchen is a classic rookie move, I did the same thing with a piece of 1095 and ended up with a nice pile of shrapnel. For 5160 I've had the best luck with regular old hydraulic oil, 10 weight, it's thick enough to slow the quench just right. Although I did accidentally use 30 weight once and the thing came out looking like a banana, so there's a sweet spot. At least you didn't try quenching in motor oil while your wife was watching, the smell alone will get you a permanent spot on the couch.

jessicaw541mo ago

My buddy Mike actually went through something similar with an old leaf spring he found at the junkyard. He was using vegetable oil from his kitchen too and kept getting these hairline cracks no matter what he did. Finally he tried some old transmission fluid he had sitting in a bucket and it worked like a charm, the steel came out way more consistent. @gavine41 is totally right about hydraulic oil though, Mike switched to that after the tranny fluid ran out and said it was even better for 5160. The cracking stopped completely once he got the right thickness for the quench.