Cotter Pin

A cotter pin is a split wire fastener with a looped head and two legs that are bent after insertion. It is used to retain a castellated nut, clevis pin, shaft, or similar component by passing through a cross-hole. The legs are spread after insertion, creating a mechanical stop that prevents the retained part from moving axially. This product is classified as a component in the fabricated metal product manufacturing industry. Typical materials include low-carbon steel, stainless steel, and copper alloy by application. The applicable standard is ISO 1234:1997, which serves as a procurement and verification reference. Buyers must specify the standard, nominal diameter, length, head form, material, finish, hole size, and replacement policy. Safety and load values must be confirmed against the selected product standard, approval, drawing, or test report; they cannot be inferred from appearance or nominal size. The RFQ should also state quantity, packaging, inspection, and traceability requirements. This product is a single-use retention element; replace after removal unless product instructions state otherwise. Surface finishes may include plain, zinc-plated, passivated, or material finish. Always verify model-specific values and standards with the legal manufacturer or supplier before use.

The cotter pin operates by inserting its two legs through a cross-hole in a shaft or similar component. After insertion, the legs are bent outward, typically around the shaft or against a nut, to create a mechanical stop. This stop prevents the retained part from sliding off or rotating, depending on the application. The spreading of the legs increases the effective diameter of the pin, locking it in place. The pin must be properly sized to fit the hole and provide sufficient retention. The working principle relies on the deformation of the wire, which is why it is considered a single-use fastener. The mechanical stop is effective only if the legs are bent correctly and the pin is made of a material with adequate strength and ductility. The exact load capacity and safety margins depend on the specific product standard and application conditions.