| 摘要 |
<p>The invention concerns a solid step drill that comprises two cylindrical sections (4, 5), a first one (4) of which extends rearward from a front tip (2), has a first diameter (D1), and transforms via a step (6) into a rear section having a greater diameter (D2). The tip (2) of the step drill includes two primary cutting edges (9), which co-operate with a chip flute (10) each that is countersunk not only in the first section (4) but also in the second one (5) and intersects the step (6) while forming a secondary cutting edge (18). According to the invention, adjacent to at least the individual, secondary cutting edge (18), a chip breaking recess (19) is formed between the cutting edge line of the cutting edge and the appurtenant chip flute surface.</p> |
