Quote Originally Posted by JAZZCNC View Post
Certainly worth a read but what helps with rotating nut is to get shortest length Nut possible.
It's also critical that the Shaft as a Flange which is machined perfectly concentric to the Nut otherwise concentricity to the screw is misaligned so causes big vibrations.
What's the thinking behind the shortest possible nut please?

The concentricity is an obvious thing and might rule out some of the cheaper offerings if my experience on the machine I've just completed is anything to go by. Having set everything up and got it working smoothly I thought I'd spin one ballnut through 180deg to get better access to the lube nipple. Major fail, that side of the axis got really stiff, it turned out that the casing/flange of the ballnut was something like 1 or 2 degrees out of alignment with the axis of the screw.