Hand Tools Archive

PEC Square Accident, Tempering Steel ?

William Duffield
By now, I think you know I'm a fan of PEC machinist squares, from Harry Epstein, for their accuracy and their very reasonable prices.

Last night, however, I experienced a problem that I have seen reported a couple of times on the woodworking forums. I was working in a very cold shop (high 30s Faranheit) in a heavy coat, and my coat sleeve managed to brush my 6" double square off the bench and onto the concrete floor. The ping when it hit was at a higher pitch than I wanted to hear, and the blade and head were laying separately on the floor. The end of the blade clamp, which was obviously more brittle than optimum for the application, had snapped off.

Harry Epstein carries replacements and I immediately ordered one. There is a link to the square itself at the bottom of the page in the link below.


Not unexpectedly, shipping was more than the cost of the blade screw assembly. Curiously, while Harry Epstein notes that the squares themselves are made in the USA, the replacement clamps are labeled "import."

When the new one arrives (being practical, I ordered two so I would have a backup) I would like to lessen the chance that it meets a similar fate. (No, I don't think a wooden shop floor is in the near future.) I need some advise, because I don't know much metallurgy. I know that some steel can be tempered to increase its toughness and decrease brittleness, but how do I figure out how long to cook it in the oven and at what temperature? Do I need to leave it in the oven after I've turned it off, to cool slowly? Should I wrap it in foil? Do I need to plunge it through the heart of an enemy?

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