Abstract: A percussion boring machine for destructive replacement of buried pipelines, having an opening-out cone at the back of the machine housing and cutters spaced in front of said cone, wherein the cutters form part of a breaking-up head slipped on to the housing and the opening-out cone is likewise slipped on to the housing.

Abstract: In a self-propelled ram boring machine, in particular for making earth bores, having a striking tool at the leading end of a cylindrical housing, a striking piston movable to subject said striking tool to ramming blows, said striking piston being driven with pulsating, translatory working strokes, the striking tool is mounted in the housing to rotate about the axis of rotation and comprises kinematic means cooperating with the housing to change a translatory movement following each blow of said striking piston into a gradual rotary movement, and pneumatically operable means for initiating or interrupting the rotary movement.