| 摘要 |
This excavating tool is provided with: a casing pipe which has a cylindrical shape about an axis and has a step part with an inner diameter smaller by one step formed at the inner periphery of the leading end thereof; an inner bit which has a contact part that is capable of coming into contact with the step part and formed at the outer periphery thereof, and is inserted into the casing pipe from the back end side in the direction of the axis so that the leading end thereof protrudes from the leading end of the casing pipe; an engagement protruding part which is provided to be protrudable and retractable at the outer periphery of the leading end of the inner bit; a ring bit which has an annular shape and is disposed around the leading end of the inner bit protruding from the leading end of the casing pipe; and an engagement recessed part which is formed at the inner periphery of the ring bit. When the engagement protruding part protrudes to the outer periphery side and engages with the engagement recessed part, the ring bit is locked to the inner bit so as to be rotatable integrally therewith about the axis toward the direction of rotation during excavation and unremovable to the leading end side in the direction of the axis. When the engagement protruding part retracts to the inner periphery side, the ring bit is removable to the leading end side. |
