Method and device for machining cracking groove for connecting rod

A method and a device for machining a cracking groove for a connecting rod, wherein a drive pulley (72) is rotated under the driving action of a rotatingly driving source (68) installed in a body (14) to transmit the rotatingly driving force of the drive pulley (72) to a driven pulley (74) through a drive force transmission belt (76) so as to rotate a groove machining part (24) integrally connected to the driven pulley (74). In the groove machining part (24), a spindle (34) integrally connected to the driven pulley (74) is rotatably supported on a support part (32), and a metal saw (36) having a plurality of blade parts (54) on the outer peripheral surface thereof is installed on the holding part (48) of the spindle (34). A first groove (88) of roughly V-shape in cross section is formed in the large end hole (20) of a connecting rod (18) by inserting the metal saw (36) into the large end hole (20) of the connecting rod, and a second groove (90) of roughly V-shape in cross section which is symmetrical with the first groove (88) is formed in the connecting rod (18) at a position opposed to the first groove (88) with respect to the axis of the connecting rod.