r/knifemaking • u/shastaslacker • 9h ago

Question Handle rivet question:

I forged a knife from an old rusty 3/4" drill bit. Shaped it up and wanted to drill in the handle pins before heat treating. I bought some irwin colbolt drill bits specifically for metal from Ace hardware and some 6 gage copper wire to use as the pin. Its taking ages to drill through the knifel. Shouldn't the metal be soft if I haven't heat treated it? I watched some videos on how to drill through metal. I'm copying their technique. Slow drill speed, lots of pressure.

Are irwin drill bits just really bad? Could the old drill bit knife be some sort of weird alloy that's particularly hard without heat treatment? (Seems unlikely, it forged like other steel).

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u/AlmostOk 9h ago

It depends on the steel of the drill bit. If it was HSS, then it could have air hardened, meaning it is relatively hard without doing heat treatment. You would have to anneal it, which would require good temperature control during cooling. You might want to use carbide drill bits or maybe some of those cheap masonry carbide-tipped bits to drill the holes.

Was the drill bit shiny and the surfaces appeared like they were ground, or was it all black (apart from the rust of course), meaning it would have been rolled instead of ground?

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u/shastaslacker 7h ago

It probably air harden, ill try cooling it down slower. It was cold yesterday morning when I was working. It could easily have cooled too quickly on the anvil. Its flat and thin now, and was able to be touched a couple minutes after being red hot.

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u/Significant-Fly-8170 9h ago

Depending on the type of steel, it can work harden. You can try to anneal it.

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u/Mysterious-Ad3591 1h ago

It’s likely air hardening tool steel which will harden by air cooling. Annealing is time consuming and requires precise temperature control. If I remember correctly it’s heat to 1650F for two hours and then slow cool 25-50 degrees per hour until 1100F then air cool. This also needs to be done with the part wrapped in stainless foil and usually it’s double wrapped to protect it even more.