"Bill Schwab" wrote in message
link.net...
Harold,

Collets shouldn't be used much beyond a thou or two past nominal for
starters, and many of the tap drill sizes are not fractional----so you'd
find not many of the sizes you'd desire can be so held.

Thanks for the heads up on that one. A crazy idea: turn the shanks so
they fit? I do not have a lathe, but will probably eventually get a
small one.

Sure! Why not?

Be aware, though, that drills are (slightly) tapered, with the flutes
(induction) hardened. There's a small portion of the typical shank where it
transitions from heat treated to annealed. It can be ignorant to machine,
so stay back a bit from the flutes, and keep the shanks as large as
possible, for strength.

In spite of the protestations of the crowd that insist you must hold end
mills in end mill holders, collets, in fact, can be a better system,
particularly when you're working under certain circumstances. Both have a
place, really, but you can run a (commercial) shop with manual machines
without special end mill holders with almost no problems. If not, every
place I was employed was having a hell of a lot more trouble than they were
aware. The real push for end mill holders is sort of a CNC event. Even
the old horizontal machines used to have a collet adapter, which was used
for holding anything that was collet diameter when it was required. They
work fine, and are more precise and more positive drive than a drill chuck,
just not quite as fast and convenient to change.



The other problem,
albeit it a minor one, is that drill shanks are often quite badly
badgered
from slipping---which could complicate getting them in a collet.

Unless it happens routinely in/from the collets, I could always buy
replacements for any pose a problem.

Collet use would likely eliminate the problem entirely because of the large
surface driving the drill, and the ability of the collet to drive well as a
result. They rarely slip, although holding a Silver & Demming drill
presents a challenge, depending on how it's applied. . It's all up to
you----and the draw bar.



I
highly recommend a good hand tightening drill chuck (something like an
Albrecht), half inch capacity. They're fast and precise. If you
think
you'd want to change drills on the fly, you could even entertain buying
a
Wahlstrom. Big bucks, and sort of dangerous in the half inch size,
though.
The 3/8" capacity Wahlstrom is a sweet dream.

I have a 1/2 in Jacobs that seems excellent to me. I'm confident that I
will use it many times, but since it adds roughly 4 inches to the
spindle, it would be nice to be able to avoid it when feasible; again,
the enemies are the difference in bit/mill position, and the clearance
for a change. I do not expect to eliminate head movement and
registration problems, but I am willing to throw a little money at
things that will help make them rare events.

Bill

Yep----that's the reason I find myself using collets for drilling
occasionally, even though I have a knee mill. I'm not interested in
cranking the knee up and down a few inches for one hole, especially at my
age. It's a lot easier to change to a collet. Yet another example of
your good thinking.

Harold