A single pre-loaded nut is one that has had oversize balls installed to minimize (not eliminate) backlash. Another option is double-nuts, with some kind of spring or elastic tensioning means, though adjustability is really not worth much, as there is a "correct" pre-load for each size screw, based on its load rating (usually 10-15% of the rated load). Some of these are adjustable, some are not. The final option is multi-circuit nuts, which have more than one (usually two, sometimes four) separate circuits, and are also pre-loaded to eliminate backlash. These also sometimes have integral elastic tensioning means.
Regards,
Ray L. |