Bohrvorrichtung

1. Drilling device having a tubular outer rod means (10) carrying an annular bore-crown (42), an inner rod means (11) extending in the outer rod means (10) and carrying an inner bore-crown (43), a common advance device for both rod means, being arranged as a slide (37) movable in longitudinal direction of both rod means and carrying a rotary drive (13) for the outer rod means (10) and a rotary percussion drive (28) for the inner rod means (11), and an adjusting device (39) for varying the mutual distance between the rotary percussion drive (28) and the rotary drive (13) on the slide (37), characterized in that a tube portion (12), extending through the rotary drive (13), is fastened to the rear end of the outer rod means (10), the end (27) of said tube portion (12) being arranged behind the rotary drive (13), and in that the inner rod means (11), in the area between the rotary drive (13) and the rotary percussion drive (28), is provided with a radially projecting annular collar (35), the front end face (36) of said annular collar (35) being adapted to be set against the end (27) of the tube portion (12) by the adjusting device (39).