Abstract: The periphery of a workpiece which has already been subjected to burring is at least partially punched by a periphery punch and a periphery die. The burred portion is then further pressed by the periphery punch and a die surface including an annular portion which opposes the periphery punch while restricting the lateral movement of the workpiece by the periphery die. An apparatus for working a burred portion is made up of a metallic mold having a periphery die and a periphery punch, a lifter which is disposed inside the periphery die so as to be movable up and down relative to the periphery die, and further working device for further working the burred portion into a shape and dimension of those of a final product of the workpiece. The further working device includes a pilot pin which is projectingly fixed to a lower end of the periphery punch and a knockout which is disposed in a recess in the lifter and which has an annular portion on its upper edge.

Abstract: A muffler for a motorcycle engine including a hollow, frustoconical muffler body, a hollow sound-absorbing member snugly fitted in the muffler body and maintained in intimate contact with the inner surface thereof, and a keep member for securing the sound-absorbing member in place. The sound-absorbing member is inserted in the muffler body and the keep member is inserted therein. The keep member is pressed into the hollow sound-absorbing member by a muffler core as the latter is inserted therein, to force the sound-absorbing member against the inner surface of the muffler body in intimate contact therewith. The muffler core includes a baffle tube extending axially of the muffler body, and a plurality of discal baffle plates secured to the baffle tube to define a plurality of chambers in the muffler body when fitted therein.