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Locking Pin Types

Locking Pin Types - What Are the Different Types of Pins | Reid Supply

Unthreaded fasteners serve various purposes, and can be found across all industry branches, but they're mostly used in machine engineering and machine parts manufacturing. In most cases, these pins serve as semi-permanent fastening solutions for various pieces of equipment or machine parts that need to be secured relative to one another.

However, some production and manufacturing processes require frequent adjustments, and semi-permanent solutions aren't really suitable for such applications. Mechanical engineers and technicians turned to self-locking fastening pin types to aid quick adjustment of manufacturing equipment and processes. Here are some of the different types of locking pins:

What Is the Function of a Locking Pin?

All locking pins share the same function: to lock and secure two pieces of couplings relative to each other and prevent them from decoupling from the fastening system. However, their functionality largely depends on the type and configuration of the pin used in your application. Almost all locking pins are quick-release pins, though some semi-permanent solutions require the use of specified tools to install and remove.

How to Use a Locking Pin

The most commonly used type of locking pins are self-locking quick release pins. These usually feature a spring-loaded ball at the pin's base, which locks the safety pin and prevents its removal. Only by actuating the release mechanism, in most cases a push-button, the spring contracts and releases tension over the balls allowing users to freely remove the self-locking pin from the hole.

Besides self-locking ball lock pins, some locking pins allow for manual locking, which secures the pin in place using tools. However, the use and actuation of all types of locking pins largely depend on their specifications.

Different Types of Lock Pins

Except for a few notable variations, nearly all types of unthreaded pin fasteners can be used as lock pins.

Quick Release Pins

Detent pins are a sort of alignment pin made of corrosion-resistant stainless steel that is used to fix machine components and workpieces with the use of a push-button, as previously indicated. They're most widely utilized in the automation and robotics industries and machine manufacturing because their positive locking mechanism ensures solid component fastening.

When activated, this mechanism contracts the spring and draws the balls inside the pin shaft. When the push-button is released, the spring extends and pushes the balls outwards, reactivating the ball lock. There are two ball-lock pin types categorized by their actuation: single- and double-acting ball-lock pins. Single-acting quick-release pins are push-button operated, but double-acting pins are activated by either push or pull motion.

Most self-locking pins feature a handle, and quick-release pins usually have handles available in a D-Ring, T-Handles, or L-handles. Picking out an adequate handle shape may be crucial to specific space-constricted applications.

Pull Dowel Pins

Pull metal dowel pins are basically identical to regular metal dowel pins, but with one notable distinction — they feature internal threading that allows their removal via a specialized pneumatic tool. Unlike their regular counterparts, which are usually removed by using a hammer and a pin puncher tool, a specialized threaded tool is fastened into the pull dowel and then extracted.

This type of pulling mechanism can be used on both taper pins and grooved pins, though that is not as common as regular pull dowels. Spring pins can't really benefit from threading, given their circumferential actuation, and those are best removed by hand tools. Another type of locking dowel pins are knurled pins, which provide a better grip when installed but are trickier to remove.

Magnetic Quick Release Pins

Magnetic quick release pins are utilized in applications that require a positive stop. However, unlike ball-lock pins, these rely on magnetic axial locks used to fixate and join various parts together. Magnets in the handle or grip maintain the axial alignment and keep the locking pin in place once inserted into the hole. The retaining forces are significantly improved by smooth surfaces of the pin and the perpendicular insertion bore.

Clevis Pins

Clevis pins aren't locking pins by default; however, they do have a perpendicular bore at the bottom that allows them to be locked in place via a locking cotter pin, split pins, and hairpin cotters. However, apart from the hairpin cotter, most cotter pins require hand tools such as nose pliers to remove.

Besides being secured by a cotter pin, some clevis pins have a spring loaded toggle on the bottom, securing the pin and preventing it from sliding out. The removal is done by deactivating the toggle and simply removing the pin.

Hitch Pins

Hitch pins are basically oversized clevis pins with a handle that are temporarily used to couple two components. Unfortunately, these pins aren't of a self-locking variety, which is why they're usually secured via a cotter pin or hitch pin clips.

Indexing Plungers

Indexing plungers are used for various applications, but their primary purpose is to replicate the locked positions defined by indexing bores. These consist of a threaded body, with or without a handle or a knob, and can be composed of different high-quality materials, such as high-carbon steel, stainless steel, and several types of techno polymers.

Lynch Pins

Lynch pins are self-locking pins that are inserted crosswise as through the end of an axle or a shaft. These types of self-locking pins securely keep components from sliding off the axle. These are mostly made of stainless or high-carbon steel.

Alignment Pins

Alignment pins are used primarily with jigs and fixtures and are typically used to align the workplace with the work holder or to position relative to removable work holder parts. These types of pins are available in different shapes and sizes to suit a variety of applications.


In summary, locking pins have been used in mechanical engineering wherever there's a need for quick and rapid adjustments of various types of equipment and machinery to secure parts relative to each other. If you're looking for locking pins, check out Reid Supply, a leading supplier of industrial components offering a large selection of locking and self-locking unthreaded fasteners.