In article ,
Spehro Pefhany wrote:

On Tue, 18 Aug 2009 22:38:37 -0400, the renowned Joseph Gwinn
wrote:

In article ,
Spehro Pefhany wrote:

On Tue, 18 Aug 2009 04:22:33 -0700 (PDT), kfvorwerk
wrote:

On Aug 17, 6:17*am, 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). *

Is this for jewelry?

Only indirectly. Among other things, it helps find certain kinds of
very hard glittery objects under the ground that typically get made
into jewellery.

Niobium jewelry is becoming popular. I'd check
the finding suppliers to see if there's anything being made you can
use.
Karl

Thanks, Karl, I've asked for a piece of the real stuff. They say the
really pure annealed stuff is gummy, soft *and* abrasive and requires
large rake angles to turn.

With the right tooling it should be feasible to do this on a CNC
lathe, but I think it might cost a couple thousand for the tools (not
a problem, if it works).

Does it need to be solid niobium? I've been reading articles from CERN
about their success in using niobium plated components in accelerators.

Joe Gwinn

Hi, Joe--

You're right, it probably doesn't have to be from a superconducting
pov, but there's some worry about the CTE match with almost 300°C
temperature swings-- could make it fail or work loose.

I'd google around the CERN website. They have to have dealt with this
issue too. I'm guessing that the base metal upon which the niobium is
plated has about the same CTE, if only so the plating doesn't peel off.

CERN did it for the money - the base metal was far easier to fabricate
than niobium, and plating saved on material costs as well.

Joe Gwinn