| 摘要 |
PROBLEM TO BE SOLVED: To prevent breakage and deformation to a front adapter or a casing pipe when excessive impact force works without degrading the impact force given to an excavating bit from a rod adapter in a double-piping bit type excavating tool. SOLUTION: This tool is provided with a cylindrical front adapter 7 mounted on the rear end part of a casing pipe 1, and a rod adapter 8 which is inserted into the front adapter 7 from rear end side, formed with an excavating bit 4 at its front end, and is connected to the rear end of a rod 2 inserted into the easing pipe 1. A cushioning member 10 is provided between the rear end surface 7B of the front adapter 7 and a surface 8C directed toward the front end of the front adapter 8 facing the rear end surface 7B.
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