Abstract: A drilling or milling head, especially for printed circuit board milling machines and/or engraving machines, having a collet chuck (11) which can be actuated by a rapid change mechanism and which is driven by a transmission. The collet chuck is opened by an axial displacement relative to a clamping sleeve (50), with the force necessary for the displacement being transmitted via a friction clutch. The transmission includes a ball bearing (9) whose balls (12) are moved around a common axis in a concentric manner by a driving part (6) fixed on a motor drive shaft (5). In addition, the balls are mounted between two bearing surfaces (13, 14) which are aligned in a concentric manner with regard to the axis and which have a circular cross-section. The balls are at least partially engaged with the bearing surfaces in a positive manner.

Abstract: A drill or milling head (1), especially for printed circuit milling machines and engraving machines, including a collet chuck (27) which can be actuated by a rapid change mechanism. The drill or milling head includes a drive shaft which can be connected to a motor (3a). The collet chuck (27) is opened by axial displacement opposite a clamping sleeve (29), and the force necessary for the axial displacement is transmitted via a friction clutch (19, 23). As a result the drill or milling head cannot be damaged, and there is no danger of injury when changing the tool if the user fails to turn the motor (3a) off beforehand.