Radial preloading is an option only for lead screws. The sectioned nut can then be tightened in the radial direction, pressing inward and meshing tightly with the screw threads. This is often done using a ramped sleeve to bear on a ramped nut exterior. The sleeve is axially loaded by a compression spring. Plus, the sectioned nut has a lower integrity, and may be prone to excessive strain, especially in the torsional direction.
Lubrication is pretty much required for ball screws if they are to have a reasonable life.
Lead screw mechanisms involving bronze nuts need lubrication as well, and it is often a thick, damping grease. However, additional lubrication can increase the load capacity and extend the life. Ball screws are prone to a certain amount of noise because of the ball bearing recirculation. Radially preloaded lead screws employ axially sectioned nuts that are forced into the flanks of the screw for a close mesh. A common method presses the nut inward with a ramped sleeve loaded by a compression spring.