Abstract: A cassette pulley is assembled from a flange part having three assembly pins which are received in corresponding holes of a hub part. The hub part has a number of reinforcing ribs which divide the bottom of the hub part into a number of recesses which are conveniently employed to hold the hub part on a group of hub holding stub shafts during assembly. Because there are more recesses than holding stub shafts, the hub may assume more than one orientation relative to the stub shafts. In order to achieve proper relative orientation of hub and flange, the hub holder is formed with a hole that is aligned with one of the hub holes when the hub is in one of a selected group of orientations. Optical sensing of such alignment enables the flange to be positioned in an orientation appropriate for assembly of the flange pins into the hub holes.