Powered hand tool, in particular a hammer drill and/or percussion hammer

A hammer drill has an air-cushion percussion mechanism 13 which includes a piston 17, that is oscillated by motor (11) via an eccentric gear mechanism 12. The mechanism 12 has a radially projecting dog (32) (e.g. a ball) on the end of a pin (34) received in the piston 17 and a drive member (e.g. gear 26) which is rotationally driven about axis (30) running perpendicular to the longitudinal centre axis (21) of the piston (17). At a radial distance from the axis (30), drive member 26 bears a driving device (31) (e.g. a bore 38) engaging on the dog (32). The ball (36) is located in freely pivotable mariner in the bore 38. For length compensation, the ball (36) is axially displaceable in the bore (38), or the dog (32) is displaceable relative to the piston (17) in the radial direction. The drill is compact, inexpensive and has only a few, and in addition simple, components (Figure 1). The drive member may be a radial lever or a disc mounted on a rotatable spindle 29. The dog 32 may be designed as a spherical pivot bearing instead of as a ball.