This is just a guess, but some electrical switches use a silver alloy as it lasts longer than the copper contacts. I think these are used in high amp frequently cycled applications and perhaps the silver tip set screws are used for these things.
There is such as thing as *nylon* tipped setscrews -- a steel body, but a nylon insert into a drilled hole in the end. That way, you don't risk the head stripping out.
If you want to make your own (a real pain drilling that hole in the tip of the setscrew), use the nylon cord used in weed whippers.
Also -- you can have a brass insert just the diameter of the thread's ID or slightly smaller ahead of the setscrew tip if the hole is deep enough. The major nuisance is that the inserts can fall through when you withdraw the thing being clamped -- unless you have the hole a bit smaller after the threads, and put a rim on the brass so it can't fall through.
Enjoy, DoN.
DoN,
Agreed that nylon tipped is probably better than all nylon, unless the nylon set screw has a larger contact area than the metal+insert screw?? It is worth buying both.
Some more fiddling revealed that I can get away with one setscrew per ring, vs. the three I thought would be necessary. That simplifies things greatly, hopefully reducing the likelihood of damage. With hindsight, I would like to undrill the extra holes. That won't work, but a die grinder followed by sandpaper got pretty close to it.
I did an informal dog and pony show for my customers/partners in this, and they seem pretty comfortable with the risk level. There is also talk of getting a loaner of the expensive part, allowing it to be installed and removed once vs. once per experimental run. That would be great, as any cosmetic damage would occur during mate/demate, not during use (absent stupidity).
Thanks to all for the suggestions!
Bill
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The nylon tip tends to spread out to maximum contact area if you crank down on it. For that, it needs to extend a bit more beyond the tip of the metal screw than would otherwise be necessary, so there is still some nylon between the metal of the screw and the part being clamped. At some point, it will expand out enough to fill the threads beyond the screw and turn with the screw as you loosen or tighten it.
Note, BTW, that the previous suggestion about making your own could also be done with rubber -- drill it to fit O-ring stock of the appropriate dimensions -- but I think that is more likely to eventually have the rim of the hole scar the expensive object.
Undrilling holes is one of many things that a welder is for. :-)
You only need three equally-spaced holes when you want to suspend something in the ring without ever touching the ring. In that case, you can use long setscrews and fit nylon cups over the end of the screws where they touch the held object.
Great!
I think that we're all glad to help with things like this.
Good Luck, DoN.
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