The black oxide coating is kind of like Teflon in a frying pan or chrome on
your bumper. It is like Teflon in that it allows the metal being drilled to
slide rather than stick allowing the built up heat to be carried away in the
chip rather than stay in the bit. It also helps resist corrosion better
than plain steel.
About the time I had mastered getting the toothpaste back in the tube, then
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