from what i've seen the end of the ballscrew is threaded either internally or externally and a cap screw and retaining plate is used to hold the bearing onto a journal, or simply held on with a nut on an external thread.
Obviously this depends on the quality of the bearing for backlash removal, and is not much good for heavy loads as the bearing is designed for radial loads not axial loads.
If you want the correct method then you need two opposing angular contact bearings in a housing.