Image Number 5 for United States Patent #7641001.
A tool for boring has an axle for drivingly linking at a first end to a portable rotatable machine. At a second end, the axle has a shaft-receiving bore into which a nose shaft is inserted. The nose has a cutting tip and a flight cutter that aligns with a flight on the axle. An insulator is electrically interposed between the cutting tip and the nose shaft, thereby electrically insulating the nose shaft from the cutting tip. The flight cutter performs the high-wear cutting at the leading edge of the flight, thereby causing the flight to merely remove the soil or other particulate from the hole being formed.