On Mon, 17 Aug 2009 11:21:32 -0500, Tim Wescott
wrote:

On Mon, 17 Aug 2009 12:17:03 -0400, Spehro Pefhany wrote:

What would be my best bet for getting a relatively small quantity
(current requirement is 100 pieces) of machine screws (a couple of
sizes, like 6-32) made from 0.25" dia. metal rod. The material (Nb) is
soft like copper and generally nasty to machine. I'd like a Torx or
similar head so it's not as easy to screw up as a slot.

Ideas? Real screw-making machines - heading and thread forming- look
like a bit much for the purpose (thousands of pounds and many HP).

AFAIK, anything but a slot means a forming or broaching operation, and
may push you into a screw machine.

EDM might be another possibility, but it would be expensive, of
course.

Other than that, for 100ea it could probably be done on an NC lathe by
any competent prototype/small-run machine shop, if they were willing to
mess with the material. For a genuine 100, with soft material, you may
be able to form the top with a hand-made die and a mallet, but you'd
probably spend a lot of time dinking with the process before it worked.

Off the wall -- could they be cast with a simple die, as nylon screws are?

Don't think so, the stuff melts at quite a high temperature.

Why are you having screws made from depleted uranium, anyway? (:-)

It has to be a superconductor, and reasonably closely matched CTE to
other "stuff" in the physics package. ;-)