Magic Screw for Makerbot

This is a 'kit' for designing or building magic screw threads that will (hopefully) build on a Thing-o-Matic and similar hobby printers. This should enable you to build a bolt and nuts so that one nut tightens normally while the other seems to turn the wrong way as shown in this video (this is the new model data):

http://www.youtube.com/watch?v=gx_OKYA3_Iw

The ancestor model did not build accurately on hobby-type 3D printers because (I think) the geometry had atypical overhangs that could