Metric thread and screw library
Have us print this for you
PLA from £6 inc. UK delivery on letter-sized prints. We slice, print on a calibrated Creality K2 / Bambu A1, QC and post.
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.
If you just want to make a screw, as opposed to incorporating threads into a bigger design, you might check out [Machine bolt/screw/nut STL file library and generation program](https://www.thingiverse.com/thing:7337677). It has over 3000 STL files to print a wide variety of metric and imperial bolts, screws and nuts. There is also a simple GUI to generate custom sizes.
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 screw axis (I assume vertical axis). The triangle outward peak is trimmed, so the actual thread cross-section is a trapeze. The nominal…
