| 摘要 |
A screwdriver bit has a shank, a connecting portion axially protruding from the shank and a head axially protruding from the connecting portion. A stress dispersion recess is formed in an end surface of the shank. The stress dispersion recess disperses a residual stress present in the screwdriver bit. Therefore, the screwdriver has strengthened structure, good durability and prolonged life for use. |
