Abstract: The bottom annular flange of a bearing sleeve which is displaceable with respect to a support frame is applied against the ground surface around the zone of a hole to be bored. A cylindrical cutter placed around a boring mandrel attached to the operating rod of a jack is downwardly displaced only at the end of travel of the jack, driven into the ground with the boring mandrel and forms a cylindrical recess around the upper end of the bore-hole. The portion of soil which is trapped between the cylindrical cutter and the boring mandrel is removed automatically after simultaneous withdrawal of mandrel and cutter. A post can be driven into the bore-hole, cement or concrete being then poured into the cylindrical recess.