| 摘要 |
A cutting point for a drill including a body having a periphery. The cutting point includes a leading cutting lip and a trailing cutting lip and a central chisel edge extending between the leading and trailing cutting lips and defining two symmetrical drill point halves. Each drill point half includes a primary relief surface, a secondary relief surface and a third relief surface. The third relief surface is inclined at an angle greater than the secondary relief surface and the secondary relief surface is inclined at an angle greater than primary relief surface. |
