EXCAVATION TOOL

摘要

PROBLEM TO BE SOLVED: To reduce a load per unit area by a transmission face by ensuring the large transmission face transmitting a striking force from an inner rod and suppress the wear of the transmission face even when excavating a hard rock belt. SOLUTION: An excavation bit 21 having substantially bottomed cylindrical shape is attached to a tip of a cylindrical casing pipe 11 by directing its bottom part 21A toward a tip side so as to rotate around its axial line O, a device 20 capable of being inserted into and pulled out of an inner peripheral part of the excavation bit 21 freely in the direction of axial line O and rotating integrally with the excavation bit 21 around the axial line O while inserted is attached to a tip of the inner rod inserted into the casing pipe 11, and a tip face 20D of the device 20 can bring into contact with a face 21E facing a rear end side of the bottom part 21A of the excavation bit 21 when excavating.