Abstract: : To investigate the entrance damaged formation mechanism in the process of drilling of BK7 glass，the dynamic characteristics of single abrasive and the distribution characteristics of abrasives on the tool end-face were analyzed． The morphological characteristics of the chipping and the formation mechanisms of the scattered surface stripes were explored，and the depths/widths of the chippings were measured． The results showed that the joint scratches of different abrasives on the end face of cutting tools caused the lateral cracking extending beyond the boundary of the hole，leading to the uneven distribution at the entrance of hole． In the formation process of the lateral cracks，the variation of the force state of the material resulted in the formation of the scattered stripes on the chipping surface． The correctness of the relationship between damaged depth and width was verified by experiments，and the nonlinear damaged depth increased with its width monotonically．

Key words: BK7 glass, hole drilling, abrasive, entrance chipping, lateral cracks, fracture mechanics theory