What is "cotter pin"

n. A split pin, the ends of which project through an object being fastened and are bent back to hold it in place

n. a cotter consisting of a split pin that is secured (after passing through a hole) by splitting the ends apart

Cotter pin may refer to:

In U.S. usage:

• Split pin, a metal fastener with two tines that are bent during installation used to fasten metal together, like with a staple or rivet
• Hairpin cotter pin, more commonly known as an "R-clip"
• Bowtie cotter pin, a vibration-proof type of R-clip that is shaped like a bowtie
• Circle cotter, a ring-shaped cotter pin

In British usage:

• Cotter (pin), in mechanical engineering a pin or wedge passing through a hole to fix parts tightly together

This usage difference is often a cause of confusion when companies of both countries work together.

The original design for the cotter pin was designed by Dr. Rudolf Cotter in 1834. The original design employed a bolt with a hole drilled through and shank of metal placed within the hole.