Positive Locking Pins: Mechanisms, Types, and Features

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  • Huyett Marketing Department
  • 06/23/2022
Positive Lock Pins Blog Hero Image

Positive locking pins, commonly known as quick release pins or ball lock pins, are single-unit, self-locking fasteners that stay in place with a button push-and-release mechanism rather than by force exerted on the pin.
The pin’s design renders it particularly useful for applications that demand repetitive use, resistance to vibration, precision, and easy installation without tools. Positive locking pins are often found in ground support vehicles for aviation and the military, repair and maintenance settings, and even in the International Space Station.

How Does a Positive Lock Pin Work?

Before delving into details, let’s define the common names for these fasteners, as each name references a key function.
  • Positive Locking
     devices must be visible (not hidden within the application) and must not require pressure or force to stay in place or to withstand vibration.
  • Quick Release
     refers to the button component; you release the locking mechanism simply by pressing the button down, which requires little time and no tools.
  • Ball Lock
     refers to the balls (anywhere from one to four) housed in the end of the shaft; they retract when the button is depressed and lock into position on the outside of the shaft when the button is released.

Anatomy

To understand how a positive locking pin works, we need to understand the components that make up the pin.
  • Head:
     Holds the button and is available in different shapes that are conducive to unique applications
  • Button:
     Sits atop the pin head and controls the pin’s locking mechanism
  • Ring:
     Attaches to the head and is optional to use; you can connect a tether to the ring and to an element of the application to prevent loss
  • Internal Spindle:
     Moves in tandem with the button and is indented at the bottom just above the ball locks
  • Internal Spring:
     Compresses when the button is pushed and forces the internal spindle down
  • Pin Shaft:
     Houses the internal spindle and the balls
  • Retaining Ring Shoulder:
     Creates a barrier between the internal spring and the pin shaft and is housed within the head
  • Ball Locks:
     Protrude out from the pin shaft to lock the pin in place and are housed within the pin shaft at the base of the internal spindle
Positive Lock Pin Anatomy

The Locking Mechanism

To put it simply, the pin locks in its resting state and unlocks when the button is depressed. In the locked position, each ball lock protrudes out from the pin shaft because the internal spindle presses against them.
When you depress the button, the internal spring compresses and pushes the internal spindle down so the indentations align with the ball locks. This creates room for the ball locks to recess back into the pin shaft interior, which allows the pin shaft to fit into the application.
To lock the pin, you release the button, which alleviates the pressure on the internal spring. This pulls the internal spindle up, which forces the ball locks to the outside of the pin shaft and locks the pin in place.
Positive Lock Pin - Unlocked

Unlocked
Positive Lock Pin - Locked

Locked

The Tether

Tether - Positive Lock Pins Blog

Many positive locking pins – although not all – are sold with a wire ring attached to the head so the pin can link to a tether (also known as a lanyard). The tether links the pin to its application to reduce the risk of lost hardware. Huyett offers nylon, stainless steel, and steel tethers to connect with positive locking pins.

Positive Locking Pin Types

There are several different types of positive locking pins. While each type uses the same locking mechanism, the style of the pin heads differ. Each style lends itself to unique application requirements.

Common Types

Button Head

  • Appearance:
     The button sits atop a small, flat, circular head that resembles a button.
  • Use Case:
     Ideal for tight spaces that require easy access to the button.
  • Comments:
     Being the most common positive locking pin, the Button Head provides an easily accessible way to release the locking mechanism.
Button Head Pin Illustration
Button Head Pin Application

Ring Grip

  • Appearance:
     The pin head is a small platform, which is attached to a half-circle ring that protrudes above the head.
  • Use Case:
     It is good for tight spaces where an L- or T-Handle won’t fit and provides an easy grip, as opposed to the Button Head.
  • Comments:
     The Ring Handle is the most economical of the positive locking pins.
Ring Grip Pin Illustration
Ring Grip Pin Application

T-Handle

  • Appearance:
     The head protrudes from the body of the pin in a “T” formation.
  • Use Case:
     It is best for repetitive use situations that require a firm grip.
  • Comments:
     The T-Handle is commonly used in aerospace ground applications and the agricultural industry.
T-Handle Pin Illustration
T-Handle Pin Application

L-Handle

  • Appearance:
     The head protrudes out from the body of the pin like the T-handle, but only on one side.
  • Use Case:
     It is good when there are barriers in the application that prevent a full T-Handle but you still need a firm grip.
  • Comments:
     The L-Handle and T-Handle are largely interchangeable unless the application does not have the space for a full T-Handle.
L-Handle Pin Illustration
L-Handle Pin Application

Functional Considerations

As with any part, you need to decide if the positive locking pin’s functionality aligns with your application needs. Here are a few elements to consider when making that decision.
  • Easy to Use:
     The pins are single-unit parts that are easy to install/remove without tools.
  • Efficient:
     Compared to other pin fasteners, their quick and easy installation saves time and money by reducing labor requirements.
  • Fewer Buys:
     They are designed for repetitive use, which cuts down on the number of pin’s you’ll need in comparison to other pin fasteners.
  • Made with Precision:
     Positive locking pins are made from precision materials and feature precision-ground shafts.
  • Versatile:
     While the locking mechanism is consistent, positive locking pins come with a variety of head styles to accommodate unique application needs.
  • Vibration Resistant:
     Since the pins do not require force or pressure to stay in place, vibration does not affect their locking function.
  • Visible:
     Positive locking pins should remain visible; this makes them easy to insert, remove, and replace. However, this may reduce aesthetic appeal.
  • They’re an Investment:
     A single positive locking pin is more expensive than a single pin fastener of most other types. However, if they are interchangeable with those pin fasteners in a particular application, you can save money over time with positive locking pins because they are reusable and do not require extra tools.
To compare the functionality of positive locking pins to other pin fasteners, our
Three-Point Pin Features guide reviews Huyett’s selection of common, non-threaded pin fasteners. You can also check out our
Pins and Wire Forms FAQs page or our
Guide to Pin Fasteners.
Positive locking pins are simple, reusable, precision fastener pins designed for repetitive use and demanding applications.
Shop for them online at huyett.com. For questions or quotes, contact our Sales Team at
(785) 392-3017 or
sales@huyett.com.
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