Accurate thread generator?
Bolt and nut threads are not simply a 60 degree angle wound around in a helix. They have flat crests and flat or rounded roots. The idea behind that is both to increase strength at the thread root and to make the crests more resistant to damage as well as make the threads easier to screw together.
The Nutjob customizer at Thingiverse makes metric threads with sharp crests and roots. I found a chart with standard UNC, UNF and UNEF thread pitches and major diameters listed in milimeters and was able to get an almost fitting 3/8-16 thread model from Nutjob. With the sharp crests I was able to force it about 3/4 through a metal nut before it bound up too tight and broke. I didn't print the bolt 100% solid, just testing and not wanting to waste too much filament.
I need *solid models*. File formats that are a collection of faces glued together won't do for what I need. I have found some accurate CAD models to download, but they're either in Solidworks format or some format that's not solid. I did find that I can upload Solidworks to the Workbench at grabcad then download converted to STL - but the one example of a ready made 3/8-16 bolt I found on the grabcad site, converted to STL with their workbench, the 3D program* I use flat out refuses to allow it to be used for boolean subtracting or subtract chunks from it.
What would be very nice is an online or standalone program that can crank out accurate STL files for all metric, standard, BSF, BA, Whitworth, buttress, ACME, square, knuckle (used in lightbulbs and sockets) and any other kind of thread, with selectable fit class.
*Caligari trueSpace 6.6. I've used trueSpace since version 2.1. As long as I use the right settings for the scene and model measurements, it outputs perfectly functional STL that works with Cura.
