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Specific example: my bicycle takes an allen wrench (hex key) that has a centre hole in it (for security purposes, a pin in the socket prevents a normal key from being used. So I made a spare by drilling a hole into a normal hex bit.

The steel was too hard to drill, so I treated it by heating it to dull red and then quenching in water. After that, it drilled very easily, and everything worked out fine and now it won't be a disaster if I lose the original.

Except, I imagine that the treatment has left the bit in a weakened state.

The question is, what should I do to undo the treatment?

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  • Why not just purchase a complete set of security or tamper bits for under 10$, tempering black oxide has not been one of my strong suites because gauging the color when the metal is at the correct heat is tough, I quench in oil but for cold chisels I try to heat to a straw color and quench. – Ed Beal May 2 '20 at 1:12

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