jt wrote:
"John Hofstad-Parkhill" wrote in message
news
jt:

I'm pretty sure the flat on the shank of the mill is for the set screw -

as

in an end mill holder. The flat would resolve any issues that would come

up

with scoring the shank.

After years of following this newsgroup, it seems that an end mill holder
has an edge over a collet for milling. I just made some 3/8" end mill
holders for my CNC mill using 23/64" drill & 3/8" reamer.


Should I use an exact 3/8 reamer, or one that's oversize?



The commercial units are hardened, then ground true. Maybe using the
reamer would work, though. The shanks are generally .0005" to .001"
undersize. Mike a few of your shanks to see what size they are.
If you have something you can set up as a toolpost grinder, you might
ream first, and if the shanks are too tight, then you can do a very
light ID grind on it. Otherwise, you could make up a barrel lap
and lap the ID slightly larger.

Jon