| 摘要 |
A generally horizontal support table is provided including an upper surface and defining a transverse center line. A support member is supported from the table for guided rectilinear reciprocation toward and away from one side of the table in a plane normal to the upper surface of the table and the support member includes structure for supporting a rotatable chuck therefrom disposed above the upper surface of the table and in the aforementioned plane. The chuck faces toward the table and is adapted to rotatably support a drill bit. Further, a pair of abutment members overlie the upper surface of the table on opposite sides of the aforementioned plane and are supported from the table for guided movement toward and away from the plane along paths normal to the plane. The abutment members include opposing abutment surfaces paralleling the aforementioned plane and structure is provided and connected between the table and the abutment members operative to inversely and equally shift the abutment members toward and away from the plane containing the transverse center line of the table.
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