Detents

Detents are features or devices that create discrete, stable resting positions in a mechanism. They resist motion and provide tactile or positional feedback, ensuring a moving part settles into defined positions rather than continuing to move freely. Most detents rely on a recess, notch, or cam profile that interacts with a spring-loaded element such as a ball, plunger, or pin; the element engages the feature to hold position and must be overcome with sufficient force to move to the next position.

Common forms include ball detents, spring detents, and plunger detents, as well as magnetic detents that use a magnet and a ferrous ball to generate holding force. Rotary detents employ circular or stepped profiles to create indexed positions, while linear detents use grooves along a guide. Cam detents use lobes that ride against a follower to produce detent steps. Some assemblies rely on friction or edge geometry rather than a spring to create a detent.

Applications span mechanical knobs and switches, gear selectors, camera lens focus and zoom rings, selectors in audio equipment, tool chucks, and various jigs and fixtures where tactile click or stop positions are advantageous. In engineering, detents are chosen to balance detent force, travel, wear, and reliability while considering temperature, vibration, and contamination.

Limitations include added wear and potential binding, with spring fatigue or debris potentially reducing effectiveness over time. Manufacturing tolerances affect feel and engagement, and high-frequency or high-load systems may require magnetic or non-mechanical alternatives. Detents are contrasted with continuous friction or latching mechanisms when fixed discrete positions and tactile feedback are required.