Abstract: An improved air-driven ground impact borer including an air valve assembly constructed of a flexible, high-lubricity plastic material such as phenolic-impregnated linen; and a reciprocal striker including, on its posterior end, a sealing bearing in the form of a split ring made of a long-wearing, resilient, high-lubricity material such as oil-filled nylon and, on its anterior end, two or more spot bearings of relatively small surface area and made of a long-wearing, resilient, high-lubricity material such as oil-filled nylon.

Abstract: A finned impact-operated boring tool according to the invention has an elongated body with a frontally tapered nose which merged with a generally cylindrical housing. A circular array of fins project radially from the housing along the surface thereof rearwardly of the nose of the tool and near the juncture of the nose with the housing. Each fin is generally rectilinear, and the fins are spaced apart to define a series of grooves therebetween which extend in the lengthwise direction of the tool. The distance from the bottoms of these grooves to the lengthwise axis of the tool housing is greater than or equal to the distance from the tool axis to the outer surface of the housing. According to one embodiment of the invention, the fins are formed on a replaceable collar which fits over the node of the tool. The finned boring tool according to the invention has improved movement speed through the ground.