a device on hand machine tools is suggested for the transmission of torque to percussion drilling tools in which at least two rotary driving grooves open out at the end of the tool shaft and strip - shaped rotary drivers of the tool shaft engage in these rotary driving grooves and include assigned flanks , which are at least approximately planar , and in which locking members are arranged in the tool receptacle and cooperate with two recesses in the tool shaft which are closed on both sides and lie diametrically opposite one another . in order to avoid incorrectly reversed insertion of tools with driving grooves which are worn out due to intensive wear , the latter are distributed along the circumference of the tool shaft in such a way that two rotary driving grooves can in no case lie diametrically opposite one another .