The vast majority of machine threads on screws are made on thread rolling machines with multiple rolling dies around the screw being formed in the centre. This makes the thread form stronger through the flow of metal between the dies, applying work hardening to materials that work harden and deforming the metal crystal structure to align with the crests and roots of the thread profile. Very quick and cheap, about five seconds per screw/bolt including forming the head - hex/torx/pozi. ACME and buttress thread forms are machined, either with an automatic lathe or milled on a multi axis CNC. I have an OpenSCAD thread library that finishes the end off as discussed in the thread. But it’s not part of the BOSL library. I’ll dig out a link later. Roger.