Harbor Freight sells a small high speed grinder that is air driven.
It is much like a dentists drill. I got a bunch of used dental drills
from my dentist and have used them to drill out small taps. Not fast
but it works. The little air grinder is cheap and the dental drills
cheaper.

Dan



Don Foreman wrote in message . ..

EDM is the best way to do this, but a "christmas tree" carbide burr in
a high-speed (at least 50K RPM) air tool will do the job.