ok stupid idea then

Cheers, got a bit carried away there. Think I will just go for multiple or changeable pulleys then.

Jonathan
1:2 was more for the cutting speed as avg. stainless is 75mm/min so with a 5mm pitch ball screw that would only be 15 rpm. 1:2 brings this up to 30rpm so a bit smoother and as I'm after 0.1mm accuracy that will give me 8 steps head room.

Downside means that rapids are only 2500mm/min which seems a bit slow.

Servos would be best and I have quite a few motors but no drivers. hopefully this will be building the pcb mill to make servo drivers........