Cotter Pin

A cotter pin is the small, dependable fastener that keeps big assemblies from coming loose, and our cotter pins do it better, cleaner, and faster. Built for repeatable retention, each pin slides through a drilled hole and locks hardware in place so your equipment stays safe and productive. If you’re securing clevis pins, castle nuts, or critical linkages, our cotter pins deliver the peace of mind you can feel in every click and bend.

Built for Fit, Finish, and Function

Our cotter pins are precision-made split pins that prevent axial movement in nuts, pins, and shafts. Available in a wide range of diameters, lengths, and materials, they’re the go-to mechanical lock when you need a low-profile, low-cost, and highly reliable solution. 

We design for fit and finish: smooth wire forms for easy insertion, consistent leg lengths for clean bends, and chamfered tips that find the hole without fighting the workpiece. Our catalog covers everything from fine diameters for compact mechanisms to heavy sizes for agricultural, construction, and general industrial use. Add in corrosion-resistant finishes and dependable packaging, and you get a product that speeds installs and reduces rework.

To complete your assembly, consider pairing with our Low Castle Nut, Slotted Round Nut, or Shaft Nut With Pin Holes for a matched, lock-ready setup.

DIN 94 Cotter Pins

Our DIN 94 cotter pins are the industry standard for simple, mechanical locking. Each pin features two tines (legs) that pass through a pre-drilled hole; bend the legs in opposite directions and you’ve created a secure, vibration-resistant stop for components like clevis pins or castle nuts. It’s a proven, maintenance-friendly solution that’s as common on shop floors as it is in field repairs, precise, predictable, and ready for daily duty.

Materials & Finishes

Pick what your environment demands. Choose zinc-plated carbon steel for everyday assemblies, stainless steel (304/316) for moisture and chemical exposure, or brass where non-magnetic and soft-metal compatibility is preferred. Every option is manufactured to tight tolerances so the pin fits as intended and bends without brittle fractures.

Sizing & Fit Guidance

Select a cotter pin diameter that matches the hole closely for minimal play, snug is good, force-fit is not. For length, allow enough leg to protrude so you can bend cleanly around the nut, pin, or shaft (typically leaving one to three pin diameters of tail beyond the hole). If you’re working with slotted nuts, first torque the nut to spec, align a slot to the hole, then install the pin.

Where They Shine

Use our cotter pins anywhere you need a mechanical “fail-safe” against rotation or axial slide: clevis and hitch pins, slotted (castle) nuts on bearings, pivot points on linkages, hinges, levers, and light duty shafting. They’re ideal for assemblies that require visual confirmation of lock and fast removal during service.

FAQs

What is the difference between a cotter pin and a split pin?

In most industrial contexts, they’re the same thing: a two-legged pin that’s inserted and then bent to lock a component. “Cotter pin” is the common North American term, while “split pin” is widely used in Europe. (Note: this is different from the tapered “cotter” used in some old mechanical joints.)

What are the three types of cotter pins?

The most common families are: split pins (DIN 94) for general mechanical locking, hairpin/R-clips for quick, tool-less retention on grooved shafts, and circle cotters (ring-style) where a low-snag profile is preferred. All serve the same purpose, retention, but suit different installation speeds and geometries.

How to properly install a cotter pin?

Assemble and torque the joint first (for nuts, align a slot with the hole). Insert the pin fully, then bend the longer leg around the fastener’s end and the shorter leg the opposite way to spread the load; trim excess if needed. Ensure no sharp ends protrude into moving parts or snag points.

How strong is a cotter pin?

Cotter pins are retainers, not primary load-bearing fasteners. Their job is to prevent movement if the main fastener loosens, and to resist modest shear from vibration. Strength depends on diameter and material, but if your design requires significant structural load, select a proper bolt/nut or pinned joint and use the cotter pin as the secondary lock.