| 摘要 |
A cutting point (11) for a drill (10) including a body (12) having a periphery (18). The cutting point (11) includes a leading cutting lip (28a) and a trailing cutting lip (28b) and a central chisel edge (14) extending between the leading and trailing cutting lips and defining two symmetrical drill point halves (34, 36). Each drill point half (34, 36) includes a primary relief surface (30), a secondary relief surface (32) and a third relief surface (38). The third relief surface (38) is inclined at an angle greater than the secondary relief surface (32) and the secondary relief surface (32) is inclined at an angle greater than primary relief surface (30). |
