Jim Stewart wrote:

Is it considered acceptable to hold work
with a Jacobs style chuck. Specifically,
is it ok to put a piece of drill rod stock
in the chuck, mount the chuck in a rotary
table and then make cuts on the stock with
my mill?
Usually not a good idea. The taper does not take side loads well and
can come loose. I saw one if my bosses try to mill a part with and
endmill in a drill chuck once, got about 1/4" before it fell off :-) If
you have some other way to hold the chuck other than by the tapers, it
might work. If its a thread-on chuck you have to watch which direction
you are milling or you could wind the chuck off of the arbor.
There are some inexpensive collet chucks available for 5-c collets.
They work horizontally or vertically and are easilly attached to a
rotary table.

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