This is just a remix of Trevor Moseley's "OpenSCAD ISO metric thread library / functions (updated)", found here: http://www.thingiverse.com/thing:311031.I just tweaked it to work on Ultimaker 2 and Cura, as Trevor's version seemed to create spaces between model segments and the results would not print correctly. Also, Trevor's version did not seem to match actual steel nuts and bolts.I calibrated my testing against an M6 nut and several M6 bolts, plus M6 threaded rod. I did not test other sizes. YMMV.All credit goes to Trevor for his excellent library. It may or may not be exactly metric standard but it (now) is compatible with steel threading and the only OpenSCAD metric library that actually works for me. :)I have also kept the same licence as it is almost all his code anyway.(Nuts and bolt ThreadTest example, with an extra cylinder for a smooth shaft provided courtesy of DonMilne (http://umforum.ultimaker.com/index.php?/user/33340-donmilne/).