Once a cutter is clamped in an end mill holder, the holder may be
removed and then later reinstalled with the cutter remaining in
(closely) the same position. Not precise (depends on how tight you pull
the drawbar), but good enough for may purposes. certainly far more
reproducible than collets.

With collets, the cutter is just randomly (with the usual collets like
R8) located. Without some kind of 'collet stop' the cutter can locate
(longitudinally) most anywhere. Worse, as you tighten a collet the
cutter position changes substantially as the collet 'draws in' (FAR more
than with an end mill holder). You can't get the cutter back in the same
position without using an indicator or gage block of some kind. Once you
get it tight and find it's in the wrong position, you can't adjust it
dependably without loosening it, which changes it's position unpredictably.

Of course, you can adjust the spindle or mill head, but that's not
what's being discussed.

Double angle collets have the same problem as above, unless both tapers
are the SAME angle (NOT the usual case). Such collets may be more
suitable to having a 'collet stop' of some kind fitted.

And as others have pointed out, there ARE special collets that both
locate and hold end mills properly, but again that's not what's being discussed.

Dan Mitchell
==========

ATP wrote:

Gary R Coffman wrote:
On Wed, 06 Aug 2003 22:54:44 GMT, Bradford Chaucer
wrote:
My question is whether a collett is sufficient for holding endmills
or am I advised to opt for the end mill holders??

End mill holders are designed to hold end mills. Collets are
workholding devices. That said, you can use a collet to hold an end
mill. The problem is that there's no way to lock the end mill in the
collet to prevent it from sucking out while cutting. That could ruin
a work piece in which you'd invested a lot of time. You can probably
get away with it indefinitely on a small machine taking light cuts,
but it is something to consider.

Gary

Are double angle collets any better? I'm getting a set of DA400 that I plan
on using with my Nichols Miller so I don't have to disassemble the drawbar
to change endmill sizes.