A control sleeve (3) is arranged in an axially displaceable and rotatable manner on the periphery of the spindle (1) of a reverse counterbore. The counterboring cutter (2) of the reverse counterbore is mounted in the longitudinal groove (6) of the spindle (1) in such a way as to be pivotable about an axis approximately perpendicular to the spindle axis and is spring-loaded in the swing-out direction. Starting from its front end (9), the control sleeve (3) is provided with an axial slot (10) and next to it with a control recess (13) in which the spindle (1) engages by means of a control projection (14). By axial movement and rotation of the spindle (1) relative to the control sleeve (3) which is spring-loaded in the infeed direction (31) and held in position by the workpiece via the stop collar (15) during the spindle feed, the counterboring cutter (2) can be pivoted from its neutral position into a working position and back again. IMAGE
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