In article ,
Daniel A. Mitchell wrote:
DoN. Nichols wrote:

In article ,
Daniel A. Mitchell wrote:

[ ... ]

The chuck doesn't even need to be loose in this case. An ordinary drill
chuck will NOT grip the hardened shank of an end mill (drills have soft
shanks). The chuck jaws must deform and indent the tool shank (not
visibly) in order to grip to it, and a milling cutter is too hard to
deform enough to provide a useful grip.

Thus a chuck should never be used to hold a milling cutter, even in a
milling machine.


Except that Albrecht makes a special version, with either an R-8
shank or one of the NTMB tapers, which has diamond impregnated jaw
faces, and which *can* grip a hardened shank end mill.

[ ... ]

Agreed ... but I DID say an "ORDINARY" drill chuck!

That you did. I just felt that I should mention that there
*are* exceptions to just about every rule, and I happened to know of
this exception -- not that I have ever had my hands (or even my eyes) on
one.

And, I doubt that a
diamond impregnated Albrecht drill chuck is what someone who wants to
use a drill press as a milling machine is likely to have, or want to buy
($$$)!

Not to mention that his drill press is highly unlikely to have
either an R8 spindle or a NTMB taper one. If it did have either of
those, it would already be a milling machine. :-) (And these Albrecht
drill chucks have permanent shanks, not something attached by a Jacobs
taper, so the opportunity for unintended separation is pretty much gone,
as either of those options needs a proper drawbar to hold the shank into
the machine anyway.

Note that there is still an opportunity for unintended release.
Albrecht keyless chucks are self tightening under normal operation, but
with an interrupted cut, and with a spindle which has lots of spring
between the drive pulley and the chuck, it could wind up under load
until the chip breaks free, at which point the chuck would rotate until
it reached either another forming chip, or the end of the spring travel
in the spindle. If the latter, suddenly the chuck outer body is running
faster than the inner body, an action which tends to loosen the grip of
the chuck. (I remember some years ago we spent quite a while here
trying to figure out why an Albrecht chuck in a mill was releasing
whatever it was holding.) The Albrecht catalog shows that they also
have a version of the chuck which is designed to prevent this problem,
as well.

Enjoy,
DoN.
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