Metric thread and screw library

I needed a large screw thread and nut to fit over a tube. There are excellent libraries for this, such as https://www.thingiverse.com/thing:8793 and https://www.thingiverse.com/thing:193647 , but I thought it would be fun to build my own.

This library lets you make metric screws. The thread geometry follows metric standards, as described in https://www.machiningdoctor.com/charts/metric-thread-charts/#c-mc . See also http://www.apollointernational.in/iso-metric-thread-chart.php for ISO thread tolerances.

Before I lead you astray, I should mention that OpenScad libraries page (https://openscad.org/libraries.html) has a number of libraries that provide various screws and nuts. In particular, check out BOSL2, BOLTS and threads.scad module. I haven't tried any of them, but they are an excellent place to look if this library doesn't do what you need. Or even if it does!

Idealized metric thread cross-section is an equilateral triangle, where one triangle side is laid along the scr