Rotating Ballnut - design ideas

[Jonathan]

Very nicely done

Thanks :). I hope it works well after all this... I modified irving's spreadsheet to include pulleys and used it to model this setup. Looks like, with the 3Nm motors I'll get at best 7500mm/min rapid and 2000mm/min with 50N cutting force. Both of those are a lot lower than the prediction for the Y-axis, 18100mm/min and 8200mm/min. All of those figures are with a 3x safety factor on the torque, so fingers crossed it might be better!

I'm currently making a mandrel from 35mm steel bar to hold the shaft in the rotary table/4th-axis to mill the pulley teeth on to it.