| 摘要 |
Core drills, with external cutting edges fastened to the periphery of a cutting-edge holder and at least one internal cutting edge which projects into an inner bore of the cutting-edge holder and the action of which together with the feed of the cutting-edge holder produces a core lying inside the inner bore, serve to produce relatively large bores with relatively low cutting capacity. When the core drill pierces through the material to be worked, there is the risk of the internal cutting edge or the internal cutting edges available being damaged by the now freely movable core or at least being impaired with regard to their effectiveness. To avoid the disadvantage described above, the invention proposes to equip the cutting-edge holder (2) with a core draw-off device which exerts an elastic draw-off force on the core (7), which draw-off force is directed away from the at least one internal cutting edge (6). The core draw-off device can consist in particular of several draw-off elements (8) which act on the core periphery (7') via preloaded supporting elements, preferably in the form of balls (9). <IMAGE>
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