Nema 17 Stepper 25mm driver pulley

This driver pulley should go perfectly with my 608zz Idler Pulley and stand (http://www.thingiverse.com/thing:155018). This driver pulley would attach to the stepper motor at the bottom and align with the idler pulley at the top to offer nicely parallel strings top to bottom.

This was drawn in Sketchup (which is not known for being good at drawing spirals. Please let me know if it works at all.

The idea with this pulley is to wind string around it (about 0.8mm thick). For my Delta, I would