Align the pin on one Single slice with the matching pocket on the other Single slice. Install the desired amount of #2-28 screws to hold the pulley slices together. Be sure to tighten the screws fully. There should be no gap between the pulleys when they are assembled.
Note: Screws can be omitted if the slices are constrained by collars or snap rings.
A piece of 1/2" OD Hex can be used to line up the parts during assembly.