cottered

Cottered is an adjective used to describe components or joints secured with cotters, a type of fastener such as pins or wedges inserted through aligned holes in the parts being joined. The term is common in mechanical engineering and historical machinery, where cottered connections indicate that a joint is held together by cotters rather than bolts, rivets, or welding.

In practice, a cottered joint involves cotters passing through holes in two mating members to maintain alignment and secure the connection. Depending on the design, the arrangement can be relatively rigid or allow a limited range of angular or axial movement. The specific geometry and number of cotters determine the stiffness and serviceability of the joint.

Cottered joints were widespread in 19th- and early 20th-century machinery, including steam engines, agricultural equipment, and some locomotives, because cotters offered a simple, economical method for assembly and disassembly for maintenance. As engineering practices evolved, bolts, rivets, and welding largely supplanted cottered connections in new designs. Nevertheless, cottered terminology persists in historical engineering literature and in the naming of older components that retain cottered fastening.

Etymology generally traces cottered to cotter, a pin or wedge used to secure parts, with the -ed suffix forming an adjective or past participle.