Making screws from soft metal

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. 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.

Assuming that it's sufficiently unpleasant to machine. If you can manage to find a way to cold form the heads, then roll forming the threads would be relatively simple.

Mark Rand RTFM

Possible change in design: a threaded rod, a washer and a nut on top.

Great, now I have to figure out how to make/get made special Nb nuts and Nb washers, as well as Nb threaded rod.

;-) ;-)

Best regards, Spehro Pefhany

Thanks, Mark. That definitely sounds like a possibility. I see tooling available for CNC thread rolling and rotary broaching of the hex/Torx.

Best regards, Spehro Pefhany

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.

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

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

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

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.

Best regards, Spehro Pefhany

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

Try milling two crossed slots and then pounding a Phillips bit into the center to swage out a Phillips recess.

jsw