Summary

This Pulley was designed for milling, but can also be printed on 3D printers. Pulley consist of two nearly identical parts. One part has slightly larger holes. Material for milling is 1/4" thick Acetal sheet.

Bore size: 5mm

Instructions

Consult with PDF drawing for part numbers / BOM and exploded assembly view.
Hardware - M2 set screws and nuts, also #2 sheet metal screws.

For 3D Printing everything is here.
For milling you would need 3 Axis CNC mill or router. You need cutter not more than 1.2mm in diameter to make accurate outline of working surface. I used 3.175mm, 1.5mm and 1mm endmills to speed up removal of the material for mass production, but whole thing could be milled using just one small cutter, if you don't mind waiting little longer.
Obviously, you need CAM software to generate G-Code for you particular machine an tooling.

GT2 Timing Belt Pulley for Milling or Printing