Simon's hex coupler
by Wired1, published
Few more mods to Eric's awesome coupler idea. Made it hex shape so you can get a shifter (adjustable spanner) onto it - and yes it can take the torque, also added three grub screws at the top. This prints side-ways without the need for supports and came out really well.
Just print it.
3 perimeters, 3 layers, 0.35 nozzle, 0.25mm layer height, 25% infill at 90 degrees fill angle.
Motor end is printed at 5mm so clean it out with a 5mm drill.
Threaded rod end is printed at 9mm so should be a comfortable fit as it comes off the printer.
M8 nut fits inside the open end of the hex coupler.
Run another M8 nut up from below with a washer and tighten it as much as you dare.