发明授权
US4207954A Core bit having axial conical core breaker 失效
芯轴具有轴向圆锥形断路器

Core bit having axial conical core breaker
摘要:
A drilling tool comprising a body having a leading face with a central recess providing the body with an annular leading cutting edge such that during drilling a central core is formed, and a central cone positioned axially in the recess for breaking up the core.
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