What is a Detent?

B. Turner

A detent is a device used to stop an object from rotating. It may also refer to the process of halting rotational movement. The classic gambling wheel serves as an effective example of this principle. As the wheel rotates, a plastic or wooden object clicks between the pegs at the wheel's edge, eventually stopping it from moving. In this instance, detent may refer to the process of stopping the wheel or the plastic device used to stop the wheel from moving.

Most vehicles rely on detents to function, and cars often include some form of this device in the gear shifter.
Most vehicles rely on detents to function, and cars often include some form of this device in the gear shifter.

Depending on the application, this device may be used in a variety of ways. It can be fixed to an object located near a wheel or spindle, and used to stop the movement of the wheel. It may also be inserted into a wheel or other round object, where it can be used to fasten the wheel to another nearby device. In some instances, a detent installed in two connected wheels can be used to help both wheels rotate at the same time, or at the same speed.

Detent-based devices can be found in manufacturing and industry, as well as many household applications. Most vehicles and engines rely on detents to function, and cars often include some form of this device in the gear shifter. This device holds the car in park and prevents it from slipping into gear when not in use. A special metal plate fits around the detent in this type of application to help control its movement.

This is similar to the operation of the standard ratchet wrench. As the wrench is rotated, the detent slips into a groove within the tool. This creates the traditional clicking noise that's commonly associated with these wrenches.

Many standard appliances also rely on this type of operation. For example, a radio or stove dial that clicks on and off includes at least one detent. Additional units may be included to allow users to turn up the volume or heat level by rotating the knob to a specific point. The standard household door knob also includes a detent pin to allow users to remove the knob or change the lock.

This device may rely on spring force or positive latching to hold the rotating object in place, or stop its movement. A detent pin locks the object in place using spring force, while a ball detent provides a more permanent and secure hold. Ball-based models are often used as fasteners, while pin-based units allow for easy removal as needed.

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Discussion Comments


@SkyWhisperer - I don’t know much about gambling either, but I absolutely love the ratchet wrench! It has to be one of the most useful tools in my collection. I don’t know what I’d do without it.

Many times I’ve needed to unscrew a bolt, and my ordinary wrench simply wasn’t up to the job. The bolt was firmly screwed in and I couldn’t generate enough torque to pry it loose.

With the ratchet wrench however, I get added leverage. The détente holds the bolt in place with each twist as I progressively apply more and more force and finally remove the bolt.


I didn’t even know they had a name for that kind of thing. On the gambling wheel I just thought it was a clicking wooden thing. I would have called it a brake, but I guess everything has a name.

I’ve never been to a casino, but I did avidly watch the TV game show “Wheel of Fortune.” In that show they have that big wheel that spins on various prize amounts (or no prize at all).

Everyone in the audience breathlessly watched the détentes click as they slowed the wheel down, hoping to halt it on the big money slot. Of course other TV game shows use a spinning wheel too but that was my favorite one.

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