Abstract: A leading body for a ground drilling machine is provided which includes a main body which is tapered at a front end thereof to form a first sloped surface and a second sloped surface on opposite sides of the front end of the main body. A slant-cutting section extends from the main body substantially along the first sloped surface. And injection ports which are adapted to inject digging liquid are positioned in the slant-cutting section such that the injection ports inject digging liquid rearward with respect to a propelling direction of the leading body along an obtuse angle with respect to a rotation axis of the leading body and substantially along the second sloped surface.

Abstract: In a pilot head 20 to be used in a ground drilling machine, the injection ports 22A for injecting digging liquid are directed rearward and angularly separated from the axis of rotation N by an obtuse angle &thgr;1 (168E). With this arrangement, when digging a leading hole D from a starting pit, the flow rate of digging liquid flowing from the front end of the leading hole D toward the starting pit can be increased to efficiently deliver soil produced by the digging operation to remarkably improve the soil removing efficiency.