Cotter Pins/Split Pins - What Are They?

Cotter pins are staple aircraft hardware devices used to assemble aircraft components together safely. In this article, we shall learn more about the purpose of these pins and how they are used in conjunction with other aircraft components.

Cotter pins are essentially tapered pins or wedges driven into a hole to keep a shaft from moving axially. These pins are made from a piece of wire and have a part of their structure bent over to keep them in place. They are often used to hold other fasteners in place, like castle nuts or clevis pins. They can be relied on to secure machine components and wheels to a shaft or an axle. Cotter pins are similar to a rivet or staple pin, and they are also known as R clips, split pins, or circular cotters. Let us now proceed to learn more about these pins in greater detail.

How Do Cotter Pins Work?

A typical low-carbon steel, AN380 cadmium-plated cotter pin is used for safetying screws, nuts, bolts, and other pins. For example, in a child's go-kart, a cotter pin runs through a hole at the end of an axle in a typical wheel arrangement.

A standard cotter pin has a fat end threaded through the hole, with the split in the pin splayed out so that it does not become loose and fall out of the hole. Because these pins’ tapered shapes are generally compressed when driven inside the hole, they generate friction and prevent the pins from becoming loose.

Different Types of Pins In Aircraft

Pins in aircraft are one of the many types of aircraft fasteners which are typically used in safetying, construction, and shear applications. Apart from cotter pins, the other types of pins that are most commonly used in aircraft are:

Flathead Pins: Also known as clevis pins, they are commonly used in secondary controls with tie rod terminals that are not in prolonged operation. Such pins are typically installed with their head up so that even if the cotter pin falls out, the flathead pin will remain in place.

Dowel Pins: These precisely shaped, hardened pins are used for keeping a machine’s parts in the correct alignment. They are available in slotted, stepped, spiraled, grooved, and high-precision tapered shapes. These pins’ high friction coefficients enable them to fixate the assembly in place.

Grooved Pins: These are solid cylindrical pins containing three longitudinal grooves made of coil stock. The grooves are pressed precisely into a cylindrical body to make its diameter greater than its normal diameter. Their most significant advantage is that they can resist extreme vibration and shock, and they need only a straight-drilled hole for functioning.

Knurled Pins: Similar to grooved pins, they have serrations around the pins’ nominal diameter. These pins are typically formed by rolling while grooved pins are swaged. There are three typical configurations found in the knurled section of these pins–straight, diamond, and helical. Their nominal diameters range from- 3/32” to ?” while their lengths range from 3/16” to 3”. The serrations in these pins result in forces that hold the fasteners in place.

Apart from pins, aircraft also use bolts as fasteners for keeping disparate components together. Some of the most common types of bolts used in modern commercial aviation are MS, NAS internal wrenching, close tolerance, and AN, among many others.

Wrapping Up

Pins, bolts, and other types of fasteners are critical hardware devices for the safe assemblage and operation of a typical aircraft. Procurement of high-quality fastening hardware is of paramount importance to ensure an aircraft’s efficient functioning and overall safety. This is where NSN Sourcing comes into the picture. With our superior quality assurance protocols for all of our products, we are a reliable name in the aviation hardware sector. Contact NSN Sourcing today to get the best in class cotter pins and related aircraft hardware!


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