I'd use a 3/8" reamer, not over or under.

Failing that, I'd bore it out, which is not unlike plunging the endmill.
However I'm not sure what size hole you'd end up with. Nothing is perfect,
but most of the end mill holders I have are close enough to give a bit of
resistance (compressing the air) when inserting the mill.


"jt" wrote in message
...

"jt" wrote in message
...

"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?


Or could I just plunge a 3/8 endmill into a 23/64 hole?