| 摘要 |
The drill bit has a drilling head on a shaft (2). The drilling head has a cutting tip with flanks having an end cutting edge (7) of a cutting surface (6) with cutting edge angle (alpha) and clearance angle (beta). The flank is divided into at least two parts (11,12) or has a convex curved shape in elevation. The clearance angle, of which there can be two, and the cutting edge angle are given with respect to the plane at right angles to the longitudinal axis of the drill bit. The values of the first (beta1) and second (beta2) clearance angles can be between 20 degrees and 40 degrees and 40 degrees to 60 degrees respectively. The cutting edge angle can be between 60 degrees and 80 degrees. |
