| 摘要 |
A drilling device for producing drill holes with undercuts comprises a drill having a drill shaft with extending drill blades, a shoulder projecting from the drill shaft, and a guiding sleeve surrounding the drill shaft between the shoulder and the drill blades, the guiding sleeve having two ends provided with openings of different sizes, the guiding sleeve having a sleeve edge which forms a support for the shoulder and a wall abutment for the collar.
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