| 摘要 |
Retractable core drill bit having a hollow cylindrical body at its lower end to which a monolith core drill bit is screwed. A stop sleeve is provided on the upper end of the hollow cylindrical body, and cutting components are pivotally mounted in the middle of the body. There is a spacer in the body having an end piece on its upper end around which there is driven a guiding sleeve resting on a stop sleeve which is surrounded by a outer end piece and an outer tube. There are longitudinal slots in the body for the radial movement of the cutting components which are disposed opposite to each other in interperpendicular planes.
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