Abstract: The rock drill (9) includes a reversible rotary motor (10) and a percussion unit (11) with a percussion valve (17). Rotary unit and Percussion unit (11) are operated via separate valves (39, 46) in a control unit (34). The percussion frequency of the percussion unit (11) is coupled to the rotation rate of the rotary motor (10) in such a way that the percussion unit (11) stops automatically when the rotary motor (10) comes to a standstill. The coupling is achieved by employing a fluid driven assembly without a mechanical clutch between the rotary motor (10) and the percussion valve (17). When disassembling the drill rods a jammed thread can be shaken loose with the percussion unit (11) be manually bypassing the fluid coupling. The same is also possible in case the drill rods becomes jammed in the drill bore. With the described embodiment a simple, space-saving and cost-effective construction is achieved which is versatile in application.