| 摘要 |
<p>PURPOSE: A drill body is provided to minimize the formation of a chip jamming and a burr and reduce radial direction cutting power as well as axial direction cutting power. CONSTITUTION: A drill body comprises a front head(4) including two cutting edges. Each cutting edge comprises two partial blades(9,10). The first partial blade is included in the front end portion(8) having a front chisel edge(29). The second partial blade is extended between an outer peripheral end point(11) and a radial inner end point(12). The second partial blade is connected to the first partial blade in the inner end of the radius direction. Two partial surfaces(13a,13b) are included in a main flank(13). A second chute bottom(30) is extended to a first chute bottom and an extended portion of the first chute bottom. The second chute bottom separates a second partial surface(15a,15b) included in a second clearance surface.</p> |
