Bob La Londe wrote:
I have one drill bit that looks like its intended specifically to go in
a collet. Its got a 3/8 shank about 5/8" long and then about a jobber
length 1/4 drill bit. It is very precise. It was in a box of misc end
mills I bought at a yard sale. When I stick it in a 3/8 collet I get no
wobble at all. Its as good or better than putting a 1/4 bit in a 1/4
collet, and way better than sticking my mandrel mounted drill chuck in a
collet to hold a drill bit. I seem to recall somebody mentioned these
bits designed to be used in a mill like this.

What are they called?

| |
| |
\ /
\ /
||
||
||
||
||
||




They are sometimes called printed circuit drills in the smaller sizes.

http://www1.mscdirect.com/CGI/GSDRVS...IT4NO=79713667

John