cotter key

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Related to cotter key: cotter pin

cotter pin

cotter pinclick for a larger image
A type of split pin used to safely secure a castle nut or a clevis pin. It is formed by doubling a piece of wire, semicircular in cross section, to form a loop at one end. After insertion in a hole or a slot in a nut and through mating crosswise holes in a bolt, the ends of the pins are bent to hold them in place. This fastener is widely used in locations where service inspection is difficult and failure would be disastrous. They are also used to prevent relative motion or sliding. Also called a cotter key.