Drop-in M4 and M5 T-slot Nuts for 80/20 Aluminum Extrusion

This is a post-assembly drop-in style T-slot nut for 80/20 aluminum. This is the type of aluminum extrusion with 11mm width at the top of the T-slot, a 6mm wide opening, about 4mm deep in the bottom of the T portion, and another 1.8mm or so in the 6mm wide slit. The design was with OpenSCAD so it could be adjusted to other T-slot profiles. The drop-in T-slot nut is designed to be inserted into the middle of an extruded rod and rotated into place. It then catches in the perpendicular orientation.

Both M5 and M4 stl files are included. The M5 version is close to the tolerance limits of what will print well within the 6mm profile. The upper cylindrical thread extension in the M5 version is not as snug as the bottom portion because the wall is thinner, so if you tighten a bolt into just the upper cylindrical threaded portion of the M5 version you will NOT get a good grip. If you tighten through into the bottom of the T it will grip snugly. The M4 version is a little stronger in its grip because it has a higher thickness to the plastic which wraps around the bolt.

These are not as strong as metal nuts. I would not recommend suspending anything irreplaceable from one of these, but in tests of the strength limits I was able to suspend my 10kg printer (sorry printer) in the air from a single one of these nuts as long as it was screwed in all the way, and this worked fine for me. No guarantees on your print, but I think this can work for assembly. However you must be absolutely careful not to overtighten these. The leverage advantage of an Allen wrench plus the leverage advantage of threading can apply far more force than the weight of 10kg, and you will easily strip the threads.

Note: The OpenSCAD file uses my threading library for the threaded holes. http://www.thingiverse.com/thing:1686322

Update v2 (2017-04-16): The new threads.scad update is much more economical with the threading faces. The updated v2 stl files using this are nearly equivalent but rendered more efficiently.