Abstract: An integral cast-iron connecting rod blank having a smaller-diameter end, a shank, and a larger-diameter end with a crank opening is set on an inclined base, and the tip end of a laser beam applying device is positioned in the larger-diameter end. While a YAG laser beam from the laser beam applying device is being applied to diametrically opposite inner central wall regions of the larger-diameter end, the laser beam applying device is moved to form notches transversely in the respective inner central wall regions. Two spreading elements are placed in the crank opening, and then a tapered wedge is inserted downwardly between the spreading elements. A downward impact point load is applied to a load bearing surface of the wedge thereby to apply spreading forces to the larger-diameter end. A crack starting radially outwardly from the notches is developed in the larger-diameter end, dividing the larger-diameter end into a saddle and a cap.

Abstract: In a method of grinding ball grooves formed in a workpiece with a grind stone, the grind stone is fed in a direction of a longitudinal axis of the ball groove in a condition in which an axis of rotation of the grind stone is inclined in the direction of the longitudinal axis of the ball groove relative to a plane which perpendicularly crosses the longitudinal axis of the ball groove. An apparatus for grinding the ball groove has an apparatus bed which is movable in a direction of a longitudinal axis of the ball groove relative to a work holder for holding a workpiece, a supporting bed which is provided on the apparatus bed, a grind stone holder which rotatably mounts on a front end thereof a grind stone for grinding the ball groove, and an electric motor and a gear mechanism for rotating the grind stone. The grind stone holder, the electric motor and the gear mechanism are mounted on the supporting bed.