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.

The "not a lot of room" was the bugger for me. I modified an Atlas milling
attachment for my SB10k and managed to mill a couple of pieces. Fixturing
and rigidity were a constant problem. The lowest of the low end mill/drill's
was a gigantic leap forward.

"jt" wrote in message
...
Have a mini-lathe, am making a gadget to pun on the toolpost so I can use
the lathe chuck as an indexing head and mill sections/slots whatever.

All my mills have a 3/8" shank with a flat.

Is a 3/8 hole bored in the spindle and a set-screw good enough?

Or should I make some sort of collet and holder?

If I make a collet, what keeps the mill from slipping - just friction, or
is
there supposed to be some sort of method involving that flat?

Bear in mind there's not a lot of room...