| 摘要 |
The invention concerns a rotary boring bit, typically for coal drilling applications. The bit (10) of the invention is in the form of a hardmetal blade and includes a cutting edge (18) having an outwardly projecting gable shaped cutting formation on either side of the intended axis of rotation (A). The bit has parallel side edges (14 and 16) which extend between the cutting edge (18) and the base of the bit. In the preferred bit, the apices of the cutting formations lie in a common plane normal to the axis of rotation (A) but are unequally spaced from the axis. |
