Also known as single-start and self-locking lead screws and nuts, these have a single thread that runs the length of the screw. The nut travels only when the screw turns, so your system won't unexpectedly move when the lead screw is at rest.

Broad, strong Acme threads make these screw jacks better than ball screw jacks for heavy loads, intermittent positioning applications, and where vibration is present.