| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent an excavating bit with an excavating head configured to be laid in a diameter extended state by rotating a part thereof from being laid in a situation such that, when excavating in a horizontal or oblique direction, it cannot perform the excavation because the rotating excavating head part is returned to a diameter unextended state by its own weight or the like. Ž<P>SOLUTION: The excavating bit 1 includes a movable excavating head 2, which is fitted into a storage space 1f formed in a part of an excavating head 1a at the top end thereof so as to be rotatable about 90° around a rotation center line 2a shifted from a central axial line 1n of the excavating bit 1. The movable excavating head includes a groove 2e provided on an outer circumferential surface thereof close to the rotation center line 2a so as to extend in the direction of the rotation center line 2a, and a spherical body 1j to be engaged with the groove in the diameter-extended state of the movable excavating head 2 is energized toward the groove by a ball spring 11. The excavating bit 1 further includes a cutout groove 1m to be engaged with the base end periphery of the movable excavating head 2. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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