Adding Structure - Printing in Plastic: Build Your Own 3D Printer - page 196

Figure 12-6. Tighten the motor collar on to the lead screw.
Move the Z-Axis rail away from Part L until the motor couple is up against the inserted bearing, and
then use an Allen wrench to tighten the set screw. Tighten the set screw(s) good and tight so the couple
will not come off of the lead screw.
On the other side of Part N, push the bearing and collar up against Part N and use an Allen wrench
to tighten the collar against the lead screw; again, tighten it securely so it doesn't loosen on the lead
screw. Figure 12-7 shows the bearing and collar tightened against Part N.