What are Castellated Nuts?

Nuts are common components to a number of fastened assemblies, often paired with bolts to compress two or more objects together. Just like all fasteners, nuts can come in a variety of shapes and forms to accommodate different applications, environments, and needs. Castellated nuts, or castle nuts, are specialized types that feature three notches on one end, giving the component the appearance of a castle battlement. With their installation alongside a mating bolt or screw, castellated nuts operate as a positive locking device that assist an installation in its ability to resist loosening due to vibration.

When implementing a castellated nut within an assembly, the component is paired together with a screw or fastener that has a pre-drilled radial hole on its shaft. After the components are tightened together, a pin is passed through the notches of the nut and the radial hole of the screw. With the addition of the pin, the nut is unable to turn, ensuring that the assembly remains secure even in the face of vibration or other stressors. Depending upon the installation and chosen fasteners, there are a number of pins that may be used.

A cotter pin, or split pin, is one that features twin tines that are bent after installation in order to prevent the ability for the assembly to easily be taken apart. With an R-clip, also known as a cotter or hitch pin, a straight leg is placed through the hole to secure the nut and bolt while a profiled leg grips the exterior of the nut. Safety or locking wires are also commonly used, and such components are passed through the nut notches and bolt hole before being twisted for security.

When installing castellated nuts alongside a particular type of bolt, it is important that the nut is turned to correctly align the notch with the pre-drilled radial hole. As castellated nuts are unable to be finely tuned in regard to torque, they should not be used for high-torque applications that necessitate specific preload conditions. Generally, notches are placed in 60 degree intervals, requiring a 30 degree turn to locate and align holes of the assembly.

Depending upon the application in question, there are a number of ways in which one may choose a particular castellated nut. Typically, it is very important to consider the material that is used to construct the type of nut, some featuring characteristics that can make them highly beneficial for specific applications. When constructed from carbon, such components exhibit high strength and durability. With stainless steel, on the other hand, castellated nuts can increase their corrosion resistance at the cost of being slightly weaker. Alongside considering the material of a particular castellated nut, size is also crucial. If the particular nut is either too small or too big to efficiently pair with the bolt, then the installation will not be able to be secured easily.

If you find yourself in need of various castellated nuts, bolts, and other fastener types, NSN Sphere is your one-stop shop with everything you require readily in stock. NSN Sphere is a trusted distributor of aircraft parts, providing customers access to an unrivaled inventory of items that are new, used, obsolete, and hard-to-find. With our dedication to quality assurance and export compliance, we proudly conduct operations with AS9120B, ISO 9001:2015, and FAA AC 00-56B certification and accreditation. Take the time to explore our vast offerings at your leisure, and our team is always readily on standby to assist you through the purchasing process however necessary. If there are particular items that you are interested in, fill out and submit an RFQ form at your earliest convenience and a team member will reach out to you with a personalized quote for your comparisons in just 15 minutes or less.


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