This is a universal joint made to lock onto 1/4-20 threaded rods and bolts. I made it for a robot arm I'm designing, the rest of which will be shared when it's finalized. I've reprinted it a few times to make sure it snaps together easily but still stays together in use.
To see a description of the project it is for and a video of it in action check out the Milwaukee Makerspace blog. There is also a link if you want to vote for my project on element14:
I printed it at 100% fill from PLA with 2 shells, on a Makerbot Replicator 2 with the spring lever upgrade on a bed covered in scotch blue painters tape.
I printed these from PLA, 100% fill, 0.30 layer thickness, 2 shells.
The two 1/4-20 threaded rods or nuts you want to join
4 nuts, you can jam them, use lock nuts, or even locktite them
2 of "universal_joint_end.stl"
1 of "universal_joint_toggle.stl"
1.Drop one nut into the socket between the prongs of each end. This is a hex to capture the nut, over-sized to account for wall expansion during printing (0.45" span) so the nut should press fit in nicely.
- Put a nut onto each of the two threaded ends you want to join and run it down to make room for the rod end.
3.Screw the ends on and jam the nuts up against the ends, try to get the rod end even with the nut on the inside. If you are using locktite or another nut adhesive, add it now.
4.Rock the toggle in to place, there are slopes in the ends of the tabs to make this easier to do from straight on. Then snap the other end onto it.