"Bob La Londe" fired this volley in
:

What the heck is that. I noticed that label today on a box of
inexpensive drill bits that I had thought were Tin coated.


Bob, it could be just what it says, "Iron disulfide", better known as
"Fool's Gold" or Iron Pyrite.

There's no reason why they couldn't chemically deposit a layer of that on
the drills, and do so more easily and cheaply than a TiN coating... G

It would _look_ right, but wouldn't do a damned thing for the cutting
properties. And, because it's hard and brittle, would probably spall off
pretty quickly in use.

LLoyd