Just learned the hard way that tempering colors lie

Old timer at my local guild told me last week to ignore the straw color on small punches and go by feel instead. I figured I knew better, made a batch of three, and two of them chipped on the first hit against mild steel. Has anyone else had better luck trusting a cheat sheet for tempering temperatures over the actual color?

2 comments

2 Comments

cooper.nathan19d ago

Funny you mention that, @wadeg92 nailed it with the shop lighting thing. I used to be the guy with the color chart taped to my forge stand, thought it was foolproof. But I had a run of three center punches that looked textbook straw but crumbled on the first tap against a hardened bolt. That was my wakeup call. Now I watch for the faintest yellow, then I hit it with a file before I even think about quenching. The chart still sits there but I barely look at it anymore. It's more for show than actual use at this point.

wadeg9220d ago

Three punches chipped on me back in 2019 before I finally clued in. I had this color chart taped to my bench for years and swore by it. Then I made a set of cold chisels that looked perfect at that light straw color but the edges crumbled on the first real use. The old guy who taught me said the color lies because of shop lighting and how fast the metal heats up. Now I pull the heat once I see the first faint yellow then test the hardness with a file before quenching. Trusting your hand and a file is way more reliable than staring at a color that changes depending on the weather that day.