Detent

A detent is a device used to mechanically resist or arrest the rotation of a wheel, axle, or spindle. Such a device can be anything ranging from a simple metal pin to a machine. The term is also used for the method involved.

Detents are for example used to simply arrest rotation in one direction or to intentionally divide a rotation into discrete .

To arrest movement, the method commonly employs a small gravity or spring-actuated lever paired with a notched wheel. The lever is mounted on a point in proximity to the wheel.

The vertical angle of the sides of the notches that face the direction that rotation is desired is generally acute (45 degrees or less), so that as the wheel rotates in that direction, the end of the lever is easily lifted or pushed out and over the top of a notch. Following this, the lever drops into the next notch and the next et cetera as the wheel or shaft continues to spin.

The angle of the backside of the notch is severe (usually 90 degrees or greater to the end of the lever) so that the lever cannot be pushed up or out of the notch if wheel attempts to turn in the opposite direction. The lever is jammed between the back of the notch and its point, stopping movement in that direction against any force that the materials used can withstand. The wheel has little resistance moving in the direction desired, other than that required to lift or push the lever over the next notch.

To resist movement (or when creating incremental steps), methods are employed which include a spring-loaded ball bearing that locates in small incremental depressions, or a piece of spring steel that snaps into position on flat surfaces or shallow notches milled into the shaft or wheel.

A well-known example of a detent can be seen on the popular game show "Wheel Of Fortune", which employs rubber flippers to help disambiguate on which wedge the wheel has stopped after being spun by a contestant. Other common examples include:

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