Self-locking means that a screw drive allows a movement without the influence of external forces due to the pitch angle and the coefficient of friction (determined by sliding pairing, surface quality and lubrication). If the helix angle is smaller than the friction angle, the spindle drive is self-locking.

In principle, a distinction is made between static and dynamic self-locking. With static self-locking, a stationary threaded nut remains stationary as long as it is not set in motion by an external drive. With dynamic self-locking, a moving nut comes to a standstill as long as it is no longer set in motion by an external drive.

However, depending on the coefficient of friction and the pitch angle, it may be sufficient in the application for vibrations to dissolve an alleged self-locking and the threaded nut to move. If the application or safety requires it, a clamping device must therefore be planned.

Single-start sliding screws are usually self-locking, multi-start sliding screws, high helix screws and ball screws are not self-locking

Junaspin is happy to help with the design. Thousands of test results are documented in our database. In addition to the pure calculation, experience from “real applications” and tests can also be incorporated.