Practice of a drilling process by a conventional drill bit has shown that a chisel terminating the web of the drill bit (see FIG. 2) at the apex of a drill bit tip portion hampers a drilling process due to high resistance of a drilled material against this chisel penetration. This effect occurs due to crumpling the drilled material by the chisel 8 (FIG. 2) having negative rake angles. This problem has been overcome in a prior art drill bit tip portion shaped by two symmetrical recessions having only one common point at the drill apex (see FIG. 3). However a sharp shape of this recession comers, which are shaped through the web, promotes a brake of shaving and a further corner obstruction by pressed shaving and dust of a material drilled. This effect reduces a drill bit tip portion shown in FIG. 3 to the shape of the conventional drill bit shown in FIG. 2 at certain modes of a drilling process.
The present invention enables one to overcome this problem by forming two symmetrically displaced oval cross section grooves shaped across axial clearance faces from axial rake faces toward the apex of the drill bit (FIG. 1). The cross section of these grooves with the axial clearance faces forms extension of lips toward the drill bit apex. This extension including point at a drill apex (FIG. 1(a)) have a positive rake angle at certain conditions, and it could be considered as central cutting edges. The oval cross section of the grooves promotes bending and twist of a shaving to a conic-spiral shape which provides easy evacuation of a shaving from the grooves.