| 摘要 |
The drill bit shaft structure for an excavation apparatus has a thin-walled shaft portion formed on a hollow drill bit shaft. The thin-walled shaft portion has a thinner wall than that of shaft portions of the hollow drill bit shaft adjacent to both ends of the thin-walled shaft portion. A cylindrical body provided with an adjustable joining structure is disposed so as to envelop the thin-walled shaft portion. Both ends of the cylindrical body are connected to the shaft portions of the hollow drill bit shaft adjacent to the both ends of the thin-walled shaft portion. The direction of excavation is controlled by bending the thin-walled shaft portion and the cylindrical body.
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