Forgot to add that since you have a lathe; make yourself a short rod the same diameter as the root of the ballscrew. This is used when you reload the nut (when you buy a ballnut by itself it comes with a shart cardboard tube of this diameter inside to keep the balls from falling out. You then put the nut against the end of the screw and turn the nut onto the screw--and off the cardboard tube...
Another item you can make which helps immensely is a set of two collars that fit the OD of the ballscrew and are milled (for square body ballnuts) or turned(for round body ballnuts) to locate the ballnut exactly concentric to the ballscrew.
You put the empty ballnut on the screw; add these collars on each end of it, and now the ballscrew is in the center. This makes adding the balls REALLY EASY. Worth the time to make IMO.