This is a mostly 3D printed rotary axis for a cnc machine. I made it to use with my MultiBot CNC machine but it would work with any machine that can accept a NEMA 17 stepper motor.
It uses a pair of 3D printed gears and a 200 mm toothed timing belt to get a 3:1 reduction on the stepper motor. This increases the torque and resolution with minimal backlash. A pair of ball bearings support the shaft, and for now I am using an off the shelf 2″ 3 jaw chuck to hold the workpiece.
Edit: added files for a 3D printed tailstock.
Add a touch of super glue to the nuts to help keep them in place if they don’t fit tight in there holes.
Use a hair dryer to carefully warm up the parts if you are having troubles fitting them together. Be careful with this, it only takes a minute or less to soften things up, check often as you warm up the parts.