Tap and Die for 3D printed threads

These OpenSCAD files generate straight or tapered (pipe) threads compatible with various standards.
The example makes a 3/4" pipe nipple and a mating threaded ring.
After calibrating my printer, these print nicely and fit standard pipes and fittings nicely.
Warning: if you ask for high quality, e.g. 60 steps per turn, rendering 10 threads can take 2 hours on my computer! A simple compile and view is much faster, but may show artifacts especially at fitting ends.
I printed these with 5% i