| 摘要 |
A drill has a tip with at least two cutting edges (8,8') and at least two chip flutes (7,7'). Cutting edges on mutual sides of the axial center line (CL) have a straight unbroken contour, the central portions of which extend axially beyond the peripheral portions. The nose radius portion on each cutting edge at the periphery is confined by a number of circular segments with mutually different radii, adjacent radii always appearing with a different size. The cutting edges are preferably provided on cemented carbide inserts (9,9'). |
