Bushing for Spool (Filament) with Skate Bearing

This is a crude design made using OpenScad, based on the other Spool Bushings out there.

This one will fit onto a 1.75 inch spool, like the one I got from New Image Plastics (their 10 lb spool). The skate bearings fit nicely onto the MakerBot threaded rod (or equivalent) and provide alot less friction so don\'t have to worry too much about possible feed issues. This is related to my other changed thing (http://www.thingiverse.com/thing:3760). The hole is not exactly round, so I made it a l