This is a temporary lash-up of another 4th axis I'm working on. It's powered by a NEMA 34, 1600 Oz In stepper with a 20 tooth timing pulley. The spindle assembly is made from an Atlas metal lathe spindle running in Timken tapered roller bearings. It has a 44 tooth timing pulley on the back and a 4" 3-jaw chuck threaded onto the 1 in x 10 TPI spindle nose. The stepper motor is rated at 3.5 amps and is hooked up to my Gecko G540 controller powered by a 24v, 15 amp power supply. The software I'm using on my PC is Mach3.