Motors and Movement - Printing in Plastic: Build Your Own 3D Printer - page 221

Figure 13-11. Attach the motor with #6 machine screws, nuts, and washers.
Next, add the other piece of the motor collar to the Z-axis motor shaft and tighten with an Allen
wrench. The end of the motor shaft should be flush with the motor collar, as shown in Figure 13-12.