Cotter Pins

Cotter Pins & Split Pins — Fastener Retention Pins

Cotter pins (split pins) are safety fastening devices that lock clevis pins, castle nuts, axle pins, and shaft pins against vibration loosening or accidental withdrawal. AIMS Industrial sells cotter pins in metric and imperial sizes — zinc-plated mild steel for general applications and 316 stainless steel for marine, food, and corrosive environment use.

Cotter Pins We Stock

• Zinc-Plated Mild Steel Cotter Pins: Standard zinc-plated mild steel cotter pins (split pins) in metric sizes from 1.6mm to 8mm diameter — the general-purpose cotter pin for agricultural equipment, machinery, automotive, and general fastener retention. Zinc plating provides light corrosion resistance for indoor and protected outdoor use.
• 316 Stainless Steel Cotter Pins: 316 grade stainless steel cotter pins for marine, food processing, and corrosive chemical environments. 316 ss provides chloride and oxidation resistance where zinc-plated steel would rust or corrode. Available in matching metric sizes.
• Imperial Cotter Pins: Imperial (inch) diameter cotter pins for American and older machinery still using AF/UNC fastener systems — critical where metric cotter pins would not correctly fit the pin hole diameter.
• Assortment Packs: Cotter pin assortment packs covering the most commonly used metric sizes in a single storage box — practical for maintenance workshops and service vehicles where a range of sizes must be accessible without multiple individual packs.

Cotter Pin Selection & Installation Guide

• Correct Diameter Fit: The cotter pin diameter must provide a snug fit in the hole — a loose fit allows the pin to rattle under vibration, eventually wearing out the hole and allowing the pin to withdraw. The standard fits the pin hole in the fastener or shaft within ±0.1mm.
• Installation Technique: After insertion, both legs of the cotter pin must be spread (bent) — one leg bent back flat, the other bent forward — to prevent withdrawal under vibration. Never reuse a cotter pin after removal, as the leg metal is work-hardened and may fracture when re-bent.
• Replacement After Disassembly: Cotter pins are single-use fasteners. Always replace with a new cotter pin after any disassembly — used pins may fracture on re-bending or may have reduced retention capability due to metal fatigue from prior bending.

Australian Business, Local Supply: As a proudly Australian business since 1988, we stock locally and work with trusted local Australian manufacturers and distributors to ensure fast, reliable supply.

Expert Support: Need help buying the right product for your application? Contact our team for application-specific advice or request a quote.

See our full fasteners range including clevis pins, hex bolts and nuts, and machine screws.