In article , says...

Well ... part of this depends on the spindle taper. Some are
designed to accept R8 taper collets directly. Others (like my Nichols
again) a solid taper (NTMB 40). Still others have Morse taper, or even
B&S or Jarno, or proprietary tapers. The NTMB tapers start with a 30 (I
think), which happens to be what is in the quick-change spindle for the
Bridgeport CNC that I have. And there are adaptor cones to allow you to
use 30-taper tooling in a 40-taper spindle, which I have found
convenient.

And don't forget the Hardinge horizontals, most of which
were shipped with spindles that accept a 5C collet directly.
So finding a collet for those requires nothing more than
a short walk over to the lathe bench.

Granted that collets are not the best way to hold end mills
for heavy cuts. But hey, if I want to shift a lot of stock
in a hurry, I don't use an end mill. For that the arbor
goes in the spindle and I use a plain milling cutter.

Jim

==================================================
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
==================================================