This pulley fits a standard type L timing belt- 3/8" pitch x 1/2" wide.  It has ~5/8" bore to fit on a 5/8" threaded rod.  Of course you can easily edit it to fit any width of belt or any desired bore.  The grub screw is a 6-32 screw that is held fast by a nylon lock nut.

I printed at 30% infill, 0.25mm layers, no brim, no raft, no support material required.  I printed several test pieces tweaking the XY size compensation in Slic3r until I got the pitch to match the belt exactly (I used -0.2 mm).

The original files are shared publicly at OnShape. Try this link:

https://cad.onshape.com/documents/e2ed39c79ea74aa8bea00aa7/w/62286696ccf84c858e652954/e/78405a283fd4...