| 摘要 |
A boring apparatus is described which comprises a substantially hollow vessel with a fixed base and a rotatable base. The rotatable base is provided, at its circumference, with at least one side cutter which rotatable with the rotatable base from a first position, in which the at least one side cutter serves to cover a respective opening provided in the vessel wall, to a second position, in which the opening in the vessel wall is exposed.
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