virtue of the heavily rounded run out 37 37 39 of the respective conveyor spiral 4 39 4 34 into the drill shank 2 the ends of the conveyor spiral are prevented furthermore from having to be clamped in the wall of a bore fig4 shows the complete drilling tool with attached drill shank 2 which is represented once again in isolation in fig4 a the drill shank 2 exhibits a total length l 3 generally measuring more than 300 mm the drill shank 2 is generally joined together via a friction welding joint 31 with the cylindrical end 46 beneath the conveyor spiral 4 the diameter d 4 at this interface 31 is larger than the diameter d 5 of the lower clamping part 33 so that the drill shank is tapered over its length l 3 in the case of known drilling tools this tapering can be performed by a one piece conical structural part or by cylindrical shoulders exhibiting jumps in cross section cylindrical shoulders for the tapering of the diameter of the drill shank have the drawback in relation to a conical construction that stress peaks can be generated at each jump in diameter due to the percussive strain.