Patent ID: 7634857

Claim:
A method for forming a sprocket having sprocket tooth heads with rounded front and back sides, comprising the steps of: punching a sprocket blank from a steel plate by fine blanking, thereby forming sprocket tooth heads with rounded back sides and protrusions on their front sides; and thereafter, pressing the sprocket tooth heads between a punch and a die having opposed, rounded, sprocket tooth-engaging surfaces movable relatively toward each other in a direction of relative movement, said sprocket tooth-engaging surfaces being symmetrical with respect to a plane midway between them to which said direction of relative movement is perpendicular, thereby crushing said protrusions and forming rounded front sides on the sprocket tooth heads, and, while crushing said protrusions, causing said rounded front sides and said rounded back sides to assume substantially the same shape whereby said rounded front and back sides become symmetrical with respect to a plane midway between said front and back sides; in which the sprocket tooth heads are pressed between said punch and said die while holding the sprocket tooth heads between said punch and a reverse punch back-up movable with said punch and relative to said die.