| 摘要 |
A drill having end-face major surfaces, contiguous faces descending from the major cutting edges and flanks contiguous to the major cutting edges. Center cutting edges are formed by end-face taperings. A chisel cutting edge is between the center cutting edges. Shapes of the cutting edges are disclosed. First ones of the flanks are angled to create an outward apex angle so that the major cutting edges and the center cutting edges run at a constant taper angle. |
