The machinist behind Latherman’s Crazy Machines shares a really perplexing screw he made that only turns clockwise within its turret. When he removes the turret, however, he reveals that this seemingly single screw is actually two different screws cut and fitted together in such a way that it can only go one way. Latherman demonstrated what he did using a carrot.
Here’s how it works when you turn it left, this side would drive that surface and it will work perfectly as a thread. When you turn it in the other direction, it will pivot around this point and expand here and clamp inside in itself into the thread. That’s all.
via Boing Boing