My CNC milling machine has a weak 4th axis.
I want to attach a larger stepper motor with seriously mor torque.
However that motor has a D-shaped 8mm shaft while an XL45T10 pulley always has a 6mm shaft.
I ordered a conventional one, hoping to drill it up but it was stuck in transit (damn Hermes. An envelope would have worked better.).
So I had to design a custom pulley that could me machined without a rotary axis (less of a top guard) and fits snugly onto an 8mm shaft.
In fact, I'm 3d printing a first one and plan to do the final one with a full sized top guard on the, thus fixed, 4th axis.