A concentric tool disc on the head is indexed round it between different angular positions, and accommodates a tool to be driven. A central shaft turning on the axis (2) of the head (3) transmits the drive from a motor via a right-angle gear train to a radial shaft (16) on which coupling half (17) slides to engage with the driving shaft (18) of the tool (11) in the working position. The coupling-actuating mechanism has a rigid component (21) intersecting the head axis (2) and clear of it in the radial direction. There can be two such components situated symmetrically in relation to the head axis (2) and the radial shaft, and which are coupled at the ends to the tool-driving shaft and a drive unit (20), the latter typically being formed by a solenoid - or alternatively a ram can be used.
