Cotter Pin

A cotter pin is a fastener of simple design used to secure threaded connections.

The fastener is a thin wire rod (semicircular in cross-section) bent in the middle so that a rounded eye is formed at the bend.

To install cotter pins, slots are cut across the top of the nut’s flats, and a hole is drilled in the threaded ends of bolts.

Cotter pins are made of plain carbon steel or with electroplated zinc coating. The main types of wire locking fasteners are:

• straight;
• spring (hairpin);
• T-shaped.

Installation

Two methods of cotter-pinning are most commonly used.

1. The cotter pin is positioned with the plane of the eye parallel to the bolt axis. One leg of the pin is bent over a nut flat, and the other over the end face of the bolt.

2. The cotter pin is installed with the plane of the eye perpendicular to the bolt axis. The legs of the pin are bent over the nut flats.