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Banjo Build
vtsteam:
Simon, warping is almost always the result of uneven heating or cooling. One side increases in length from heat while the other possibly more or less plastic does not change at the same rate. When they cool, they are different lengths, and so, curved. So heating all over evenly is pretty much the way to avoid it.
S. Heslop:
That makes sense.
I've got a new problem now, I can't make a chisel/ punch that will hold an edge. Even went back to the HSS toolblank but it didn't take long for the tip to chip off. I'm wondering is perhaps the file is harder now than it was before.
vtsteam:
If it cooled rapidly, yes.
Also a lathe toolblank is not designed for impact like a cold chisel is. Start with a re-ground cold chisel and that will work better. You can use silver steel (drill rod) too but you need to harden first and then temper back down to a level that can be used as a metal chisel. Otherwise it will be too brittle.
S. Heslop:
--- Quote from: vtsteam on June 10, 2015, 02:31:18 PM ---If it cooled rapidly, yes.
Also a lathe toolblank is not designed for impact like a cold chisel is. Start with a re-ground cold chisel and that will work better. You can use silver steel (drill rod) too but you need to harden first and then temper back down to a level that can be used as a metal chisel. Otherwise it will be too brittle.
--- End quote ---
I was using some drill rod and just went back to the HSS toolblank after the drill rod didn't work. I'm not really too excited about that drill rod though. I've used it in the past and I felt it was somewhat soft even after hardening. Maybe they sold me the wrong stuff!
One source of pretty good hardenable steel i've found is motor spindles. I think I might still have one hanging around somewhere. I could perhaps use the one out of that drill I wrecked a month or so ago.
S. Heslop:
I made a nice chisel from a motor shaft. Got it hardened (the little gouge on the right was from a good few mighty strokes with a round file, it's maybe not as hard as it could be but it's still pretty hard). And the end got dulled after a couple of taps, and it didn't raise any teeth.
I think i'd conclude from this that the file is still harder than it should be. But if blocking the ends of the firebrick forge wasn't enough to let it cool slowly then i'm not sure what would be. Or rather, i'm not sure what would be practical for me.
I might maybe try running the metal melting furnace and putting the files in that, and blocking it off to let it cool. It's not hugely insulated though, using just dense refractory, and it'd use alot of gas doing that.
One other thing I might be able to try is building a long hearth out of firebrick with a coal or charcoal fire inside, and letting the files cool down inside of that.
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