Abstract: A drilling assembly which is particularly adapted for drilling in regions of the earth having permafrost, comprising a relativey large earth auger including at least one helical flight which is welded to a long central tube. The upper end of the auger has a shape such that torque may be readily applied to the auger for rotating the same. Interiorly of the upper end of the tube is a means for mounting a downhole percussion hammer, such that the percussion hammer may be suspended for operation within the tube. Preferably, a substantially solid drill bit having a generally frustoconical (pointed) shape is used in conjunction with the percussion hammer. Also, a means for advantageously providing for admitting more compressed air to the bottom of the hole than would normally be admissible by relying on air supplied to the percussion hammer alone.

Abstract: A substantially solid drill bit has a relatively flat face at its forward end; the face comprises a plurality of plateaus, preferably three in number, which are separated by radial relief channels that intersect one another near the center of the face. The sides of the body constitute a frustrum of a cone, preferably having an included angle of about 14.degree., with the narrow portion of the cone being at the base of the body. Spiral grooves extend along the sides of the body, and at least some of these spiral grooves intersect the radial relief channels. A plurality of hardened inserts or buttons are mounted on the face of the bit, and the radial spacing of such inserts from the longitudinal axis of the body is such that there is an overlap of the "track" or "trace" of each insert by the track of another insert, as the body is rotated about its longitudinal axis.

Abstract: A drilling tool assembly comprising an elongated shank having an upper end for receiving driving forces, and having tapered threads at its lower end for engaging a drill head. The shank has first and second downwardly facing shoulders, with one of said shoulders being above the threads and the other shoulder being below the threads. A removable drill head has tapered threads for engaging corresponding shank threads along substantially the full length thereof. The drill head also has first and second upperwardly facing shoulders adapted to respectively bear against the first and second shoulders on the shank. The drill head shoulders are positioned such that they are still separated from the confronting shank shoulders by a gap when the threads of the two elements initially make up along the pitch line during their assembly. The gap optimally falls within the range of about 0.010-0.