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.

Abstract: A tensioning frame (1) for stencils (9) formed of metal foils or plastic films, especially for stencil printing, provided at their margins (8) with perforations (10) for tensioning. The frame includes a tensioning device operated by a pressure medium for driving tensioning bars (5) that carry hooking pins (6) that engage the perforations of the stencil. The tensioning device is formed by an elastically deformable tensioning tube (4) disposed in a frame profile (2) and uniformly supplied with a pressure medium. The tensioning bars lie with the full length of their front sides in contact with the tensioning tube and with their back sides resting against fulcrum nubs (17) which in turn are supported against an extrusion (3) which closes the frame profile. The tensioning bars can be pivoted by inflating and expanding the tensioning tubes to stretch the stencil over a bridge (16) on the frame.