| 摘要 |
The present invention relates to a drill for drilling of metallic workpiece, as well as a cutting insert for use in this drill. The drill consists of a drill shank with at least two straight or helical chip flutes and at least two insert pockets for a substantially square central insert (16) and a peripheral insert (17). The operative edge (26B) of the peripheral insert (17) protrudes sideways such that the diameter of the drill hole is determined thereby during chip transport through one chip flute and the operative edge (26A) of the central insert (16) is provided radially inside the periphery of the drill shank (11) for chip transport through the other chip flute. The operative edges (26A,26B) of the cutting inserts (16,17)) overlap each other at an area (Z) between the rotational axis (CL) and the periphery. The operative edge (26A) of the central insert (16) extends in to and preferably a piece past the drill axis of rotation (CL). The central insert has four cutting edges (26) with rake surfaces which define at least one rake angle. The rake angle for the operative edge (26A) of the substantially square central insert (16) is larger at the area (Z) for overlap than at the rotational axis (CL) of the drill. |
