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I'm makinf a circle jig for my dremel. On the 2 rails, I'm using an UHMW plastic block, with 1/4" pivot pin underneath in the center. To lock the block to the rails, I intend to use a 10-32 brass bolt, with a little jig knob to lock er down. I assume that UHMW will hold a 10-32 thread sufficient for the task? Maybe 10-24? I might use 1/4" thumbscrews, but prefer brass for the "Dremel tool steel" rods, If ya catch my drift. They're not drill rods.

(Too tired to post pix)

Fine threads aren't as defined in materials as soft and "flexible" as this material. Unless your UHMW is thicker than 1/4", I would stay with coarse. The fine just won't survive the wear from loosening-tightening like the coarser. That is why one rarely sees fine threads in aluminum unless it is a true hardened alloy like 6061 T6. An insert might not be a bad idea-they have those coarse and deep outer threads and you would have good wear properties.

yeah, pix would've helped, but the hole will be about 3/8" I think.

I'll probably just use the 1/4 X 20 thumscrews, albeit gently. This prototype is actually probably going to get little use, as I want to machine one of aluminum like the microfence deal. I don't see myself settling for much less, seeing how easy it is to make one of a high quality

The 1/4-20s in my UHMW circle jig have seen a fair bit of use in five years, adn they are still fine. The coarse threads are better.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Yeah, there really is an art to it isn't there.