Scored a coffee can full of assorted bits at a yard sale but they have a blue hue indicating they were over heated via abuse. Is there a way to retemper them? What color should the metal be before cooling? Got 44 of them for $12.00, 5/8ths and down.
My advice is cut the off at the discolored point and resharpen them.
First they would have to be drawn abd then rehardened, a slow and long process done at controlled temps, and then you would have to contend with warpage. Not worth it.
never done a drill bit before, but if i was going to try. i would take 1of them and normalize it then heat to different stages and try and when i got to a suitable hardness versus brittleness. i would normalize the rest, sharpen then temper to the same color. probably a blue on the cutting end gradually getting softer up the shank. you'll probably have some scale to contend with but that may be easier than having to reshape a hardened cutting edge. warpage could be a problem but if just for normal holes and nothing that has to be exact, it might not be to bad.
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