Patent ID: 7673605

Claim:
A method of manufacturing a rocker arm, the rocker arm being a cold-formed rocker arm of a cam follower type and having a guide groove for accepting a top end of a valve stem of an internal combustion engine, the rocker arm for aft attachment to a cylinder head of the internal combustion engine, and for actuation of a valve of the internal combustion engine, said method comprising: punching a plate material into a predetermined shape having a bridge part and a pair of side edges; moving a punch so as to press against the bridge part of the plate material to form an initial groove having an opposing pair of guide walls by depressing the bridge part of the punched plate material by a predetermined amount in a thickness direction of the bridge part of the punched plate material; and moving a sandwich pressure punch to apply sandwiching pressure to each guide wall in the pair of guide walls in a direction transverse to the thickness direction so as to increase the height of each guide wall in the pair of guide walls, while maintaining the punch within the initial groove, the guide groove being defined between the pair of guide walls.