BikeParts Wiki
File:Cotter pin.JPG

UK cotter pin from a bicycle crank


A cotter is a pin or wedge passing through a hole to fix parts tightly together. In British usage cotter pin has the same meaning,[1] but in U.S. it refers to different fasteners.

Typical applications are in fixing a crank to its crankshaft, as in a bicycle, or a piston rod to a crosshead, as in a steam engine.

Popular usage[]

Formerly, it was common to mount bicycle crank arms using a cotter, though now usually a more easily maintained arrangement is used such as a square tapered or splined interface. These cotters have a short threaded section at the narrower end of the taper, which is used to hold the cotter in place with a washer and nut.

Because bicycle cotters were normally retained by a nut and washer, the distinction was unimportant in this context.

See also[]


  1. Template:Citation.

External links[]

de:Keil (Technik) sv:Sprint (teknik)