How to Fasten a Cotter Pin

A cotter pin is a fastener used to connect two pieces of metal, usually so that one can move freely around the other. Common applications include securing a lawnmower wheel to an axle. Cotter pins are shaped like bobby pins and work on essentially the same principle, but are made of much stronger metal. Fastening a cotter pin takes less than a minute with a pair of pliers.

Things You'll Need

• Cotter pins
• Metal parts with predrilled holes

Instructions

1. Attach the two pieces of metal to be secured. For example, slip the hole of a wheel onto an axle with a predrilled hole for the cotter pin.

2. Insert both tines of the cotter pin into the hole until the eye of the pin is flush against the metal part.

3. Hold the eye of the pin with one hand securely to the metal part and use the pliers to pry apart the tines on the end of the cotter pin so that it cannot fall out of the hole.

Tips & Warnings

• Check installed cotter pins regularly to ensure the tines are not broken and the pin is secure.

• Do not reuse cotter pins.

References

• Cotter Pin Usage and Diagrams
• Cotter Pin Size and Installation