Trunnion

Common card · No. 270451

A trunnion (from Old French trognon 'trunk') is a cylindrical protrusion used as a mounting or pivoting point. First associated with cannons, they are an important military development. In mechanical engineering (see the trunnion bearing section below), it is one part of a rotating joint where a shaft (the trunnion) is inserted into (and turns inside) a full or partial cylinder.