| 摘要 |
This excavation tool comprises: a casing pipe, a large-diameter ring bit disposed coaxially on a distal end side of the casing pipe, and a pilot bit inserted into the ring bit through the inside of the casing pipe. A bit head that expands in diameter when rotated in a tool rotation direction during excavation is provided to an outer circumferential part at the distal end of the pilot bit. Provided to the ring bit are: an engaging part that engages with the expanded bit head in the tool rotation direction and a first abutting part capable of abutting the bit head in the axial direction. |
