Abstract: In a method for making a self-propelled impact boring tool, the tool body is formed by swaging a steel tube to form the tapered nose of the tool. This results in less wasted steel as compared to conventional machining of a solid steel bar to form the body, which is the largest single part of the tool. The tool body may then be fitted with a tool anvil of slightly different dimensions than the forming anvil used during swaging to provide an interference fit.

Abstract: The weight of a pneumatic ground piercing tool of the type having a stepped air inlet is reduced and tool power increased by providing the tool body with a dual diameter. The tubular tool body has a front section and a rear section which has a greater inner and outer diameter than the front section, thereby reducing overall tool weight. In a preferred embodiment, the rear end portion of the striker likewise has a greater outer diameter than the front end portion thereof. The bearing of the front end portion of the striker remains in sliding contact with the interior of the front body section during tool operation, and the bearing of the rear end portion of the striker likewise remains in sliding contact with the interior of the rear body section. In this manner, the power of the tool is enhanced because the tool has less weight and the air distributing mechanism, located in the rear body section, is the same size as in a conventional tool wherein the entire body has a uniform diameter.

Abstract: In a method for making a self-propelled impact boring tool, the tool body is formed by swaging a steel tube to form the tapered nose of the tool. This results in less wasted steel as compared to conventional machining of a solid steel bar to form the body, which is the largest single part of the tool. The tool body may then be fitted with a tool anvil of slightly different dimensions than the forming anvil used during swaging to provide an interference fit.

Abstract: The present invention provides a self-propelled impact boring tool which, according to one aspect of the invention, has a simplified tail assembly so that the tool can be readily assembled and dissambled to allow replacement of worn parts. Such a tail assembly includes a nut and an end cap which can be secured together by a series of conventional bolts which extend into threaded holes in the nut. The nut, which is screwed into the rear end of the tool body, can be clamped in position with the screws with far less torque than would otherwise be required with a conventional, unitary tailpiece.