| 摘要 |
Drilling apparatus (50) for producing drilled holes with undercuts, with a drill (15), the drill shank (19) of which has a side cutting edge (14) protruding radially beyond the periphery (18) of the drill shank, and, on its circumference, opposite the side cutting edge (14), has a flattening, which makes possible the insertion of the side cutting edge (14) into the drilled hole, and the drill shank (19) of which is firmly connected with a connecting coupling (20), which is disposed in an articulated fashion between the drill (15) and a drill driving mechanism, permits wobbling motions of the shank as the drill (15) is rotating and has a drill shank-side coupling (29) with an axially movable indentor (85), which can be supported on an inclined plane (17) of a coupling (29) connected with the drill shank (19), which inclined plane (17) brings about the radial advance of the side cutting edge (14). In order to improve a drilling apparatus (90) with the aforementioned features in such a manner, that the drill (15), when producing a pre-drilled hole (12) in the workpiece (46), can be guided forcibly against radial motions by the axial advance of the drill (15) or pulled out of the finished, undercut, drilled hole, even when a self-alignment of the drill-shank side coupling (29) taking place as a result of centrifugal forces is not or not adequately possible, this apparatus is constructed so that the indentor (85) axially overlaps the drill shank-side coupling (29) in a position, which is not acted upon axially and is radially coupled positively with this coupling (29).
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