a material with hardness that is lower than that of the material of the pipe and striker 8 and or corresponding to the adjacent end portion 11 of the shank end 5 and has a shape and or surfaces 21 22 to compensate for the applied forces application_number US 29617199 A description a drilling apparatus 1 for two pipe strings is shown in front elevation view in fig1 an outer pipe is shown at 2 and an inner tube having a smaller diameter is shown at 3 while the outer pipe 2 is engaged for rotation with a rotary drive 4 which is not described in detail here a rotary drive motor 6 is used for driving a rotary impact driven 7 with a striker device to drive the inner pipe 3 in the rotary percussive mode fig1 shows a shank end 5 of the end of the outer pipe 2 having twin threads 14 the rotary drive 4 and the rotary impact drive 7 are axially movable together on a slide which is not referenced so that the drilling pipe strings can be driven as a whole into the rock or into a building structure the slide is divided into two parts the parts are connected together by means of a hydraulic cylinder for retracting the rotary impact mechanism from the rotary drive the outer pipe 2 and the shank end 5 should be driven not only.