| 摘要 |
<p>A core (5) tapers only as far as a space (a) from the tip of a drill bit and, in this space, has a diameter (d1), whose size exceeds the size of a core diameter (d2) in the tip. The core diameter in the tip amounts to 15 percent of a diameter (D) of a working area and a transverse cutting-edge angle (gamma ) lies in a range between 100 and 110 [deg] .</p> |
