Secure the coupling onto the z-motor shaft by tightening the two grub screws.

Make sure that one of the grub screws is being tightened against the flat of the motors shaft.

Note, the end of the motors shaft should be pressing against the end of the lead screw, inside the coupling.

Important:

The lead screw inside the coupling.

The motor shaft inside the coupling.

There should be not gap between the lead screw and motor shaft.