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After finishing my Modular CNC Controller I built this 4th axis attachment for my CNC router and my milling machine. This will let me machine parts such as gears, and carve 3D patterns wrapped around cylindrical shapes. In the Part 1 video I build the main drivetrain components, using a harmonic drive gearbox to get precise angular positioning and high torque with low backlash.
In the Part 2 video I weld and machine the steel enclosure, install the harmonic drive system, and try it out.
In this video I apply Powder Coating to the housing.
The Harmonic Drive web site has detailed information about the style of gearbox that I used. The Catalog link on that page provides detailed documentation about this family of ultra-low-backlash gearboxes.
I bought the 3-jaw front-mounting self centering lathe chuck from Shars. Any similar chuck should work, provided that it can be mounted from the front.
I bought my stepper motor on Ebay after quite a bit of searching to find one with the specs I wanted, including the 8mm output shaft to fit the coupling on my particular gearbox. Here is a link to a similar Nema 23 stepper motor on Amazon.com, but with the more common 1/4″ output shaft.