| 摘要 |
PROBLEM TO BE SOLVED: To surely perform the expansion and contraction of a hole in spite of being low cost.SOLUTION: An excavating tool 1 includes an excavating tool body 10 and a pair of movable blade parts 20, 20 swingably mounted to the tip side of the excavating tool body 10. The movable blade part 20 is swingable around a hole penetrated with a shaft part 13 and in a plane along a plane part. As a result, when the excavating tool 1 is rotated, first, the movable blade part 20 is shaken out by an inertia force and a centrifugal force, and the movable blade part 20 is further projected to the outer peripheral side by friction generated between a gauge tip 3A of its tip and the inner peripheral surface of a lower hole to be placed in an expanded diameter state. |
