| 摘要 |
Drilling head comprising a body for fastening in a mounting support. The body carries a pair of radially movable tools. A casing is mounted for axial displacement along a bore in the body, the casing being rotatable relative to the body about the axis of the bore. Structure is provided for rotating the casing in the bore and for moving the casing axially along the bore. The casing supports pins which are engageable with both tools of the pair of radially movable tools and which in one axial position of the casing along the bore move both tools in opposite axial directions upon rotation of the casing and which in another axial position of the casing along the bore contact only one tool to move only that one tool radially relative to the other tool.
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