It is known from the practice of diamond drilling that during drilling of hard fractured rocks of 1X-XP categories of drillability, the mechanism of their occurrence is explained by self-jamming of the core in the matrix ring and the drill bit body. As a rule, self-jamming of the core is associated with settling of large cuttings that, as they accumulate, overlap the annular gap between the cores and the inner wall of the core barrel and clog the flushing channels in the matrix. In such cases the normal circulation of the cleaning agent is disturbed, and in order to restore it the drilling tool has to be pulled away from the bottom hole. If this operation is not performed in time, there is a risk of burning the diamond core bit. If there are additional flushing channels in the body in case of core self-jamming, the cleaning agent continues to circulate through these channels, which prevents the tool from getting into a situation of increased wear or burning. In our opinion, it is especially reasonable to use such crowns in case of automated drilling process control; in this case the control algorithm and control over the drilling process in fractured rocks are simplified.
