Abstract: A drilling attachment for a utility truck designed for digging pole holes for ordinary utility and telephone poles is disclosed herein. The attachment is intended to replace the auger portion of a conventional auger digger when it is necessary to drill through rock or other hard materials. The excavating method contemplated employs a three step process. First, a deep kerf is cut into the rock by a plurality of drill bits that are independently driven in a rotary/percussive manner while being rotated about the circumference of the kerf. The dust and rock fragments generated by this process are removed from the kerf by an air flushing/vacuum system, that also serves to cool the drill bits. Second, a hydraulic piston is inserted into the kerf and expanded, thereby applying a lateral force to the base of the resultant core causing it to break away from the surrounding rock. Finally an expandable plug is inserted into a pilot hole located at the center of the core.