Stamping tool and method for producing an attachment piece of a wiper arm

The tool has first, second and third punching tool parts for forming a fastener (1) of a wiper arm of a windscreen wiper system. The first and third tool parts form two ends of the fastener, and the second tool part forms a central region of the fastener. Fastening units are formed such that the second tool part is removable and interchangeable against a fourth tool part, which is different from the second tool part. The first and the third tool parts form continuous openings (5, 6) in the fastener. An independent claim is also included for a method for producing differently formed attachment parts of a wiper arm.