In this video I show a project I have been working on with a friend of mine who is a hot whammy electronics guy. This setup replaces most of the old school mechanical gear train used for cutting helical features. The ratio is nearly infinitely adjustable to accommodate helical cuts found in milling cutters, drill bits, helical gears, worms, and threads. This proof of principle system was developed for making special long length magnet mandrels that are too long for most CNC machining centers. The motor is a digital servo that is synchronized with the table travel via a precision 2000 count per rev encoder coupled to the X axis handwheel.

Servo motor used. https://www.quicksilvercontrols.com/S...
Optical encoder. Disc instruments Optical shaft encoder. 8822000IBLPTTL (obsolete)