Mystery screws can be pretty hard

[ericc]

Recently, I disassembled an office chair so that it could be thrown in a standard trash collection barrel. Of course, I saved all the screws, since they supposedly will do better in my resource bin than in the landfill. They wouldn't cut with cobalt HSS, though. I thought the tool was above center, but this was on a QCTP, and the tool was already adjusted. Eventually, I got a little spark, and the tool was toast. I remembered reading on the Internet that even hardened bolts can be easily cut by HSS. Carbide would cut the screw. I took it out of the chuck and gave it a little "kiss" with the propane torch, It was completely different. Nice curled chips, smooth cut, and a good finish. The end use was for a small pin wrench. I didn't bother rehardening the pins, since the application didn't require it. That's what one has to put up with when using mystery metal.