On Mon, 17 Aug 2009 15:07:49 -0700 (PDT), the renowned whit3rd
wrote:

On Aug 17, 9:17*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). *

Main idea: convert to rivets.

Lesser ideas: heads of the 12-point style are easily driven and
formed, might
give better strength than an internal socket.

Have a design problem where the driver (but not the head) has to fit
through a relatively small hole in some cases (imagine putting the
screw into the internal side wall of a pocket, driven through a
smallish access hole), but it's certainly worth considering. Maybe a
two piece driver.

You can probably roll
threads
easily enough, the first size down from 0.25" rod is 1/4-28.

The table says yield strength is closer to stainless than to copper.

I'm told this stuff is very, very pure and annealed, and is softer and
gummier than copper. I see yields in the mid-fifties MPa on the net.
I'll try to get a chunk of rod and actually play with it.


Best regards,
Spehro Pefhany
--
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