On Nov 24, 11:11 pm, "Jeff" wrote:
Bits are coated after sharpening with a thin layer of titanium nitride which
is a hard material.

seehttp://en.wikipedia.org/wiki/Titanium_nitride for more detail.

Hmmm. Thanks for posting that link. I'd posted earlier about titanium
oxide coating, which is commonly used on knives - not sure why I
confused the two in my mind. Titanium oxide is hard, titanium nitride
is much harder. Thanks for setting the record straight, Jeff.

R