Screwy Screw

by msruggles Oct 14, 2011
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Hmm. The "trick" thread and nut work perfectly, but the real nut won't work at all. Strange. I'll try scaling up the nut tomorrow.

Filed down the large threads of the bolt a bunch, and now it works. Very cool trick, the reverse threads are much less noticeable on the physical object than in the 3D model rendering. (I printed at 50% scale)

Fun print. I had to increase the scale of the nuts 5% to get them to fit smothly.

Cool! That's my video, so I'm glad to see it got noticed!

For easier threading I suggest you bevel/chamfer the openings on the nuts, the way you did on the end of the bolt. A beveled opening also helps disguise the trick threads by recessing them away from the exterior.

For purely aesthetic reasons I also suggest you 'drill out' the center of Nut_1 so
it has approximately the same size opening as Nut_2.

Here's a collection of screws and nuts I built trying to develop my version. I will try building your version this weekend!

Can you post your STLs of the pieces in your video?

Sure! I'd been holding back the STL files to keep people guessing how it worked, but now that the cat's out of the barn I'd be happy to share. But I'd still encourage people to try to guess how it works and try making your own version as msruggles did here.

My files might be challenging for hobby FDM printers, I'm not really sure. I used an unconventional sinusoidal thread profile, while msruggles used a more typical V profile.

Tonight I built an improvement that makes the nuts look even more alike without affecting the way they work. (Only the 'c
onventional' nut was changed.)

Looks like you've gone Nuts! :)

Whew! that's crazy. This must be some kinda voodoo! :)