CNCZone – DIY 4th Axis from First Principles (quite similar to my own ideas)

Ironically, I’m not the only one who’s done this.

CNC Zone – Building a 4th Axis from First Principles

This thread post-dates my own efforts by over 26 months, but, most pleasingly, echos my own logic to a most satisfying level. He states he already has a high speed lathe function, and has chosen a differing harmonic drive, but his approach has all the checkpoints mine did, and more (such as testing the harmonic before use). Even better, he is a PhD in measurement, and this reflects well on my thought processes.

There is excellent information on bearings, building philosophies, engineering trade offs, final operations.