Patent ID: 8550756

Claim:
A drill bit having a central rotational axis and at least one outwardly-extending cutting edge, said at least one cutting edge comprising: a first cutting portion being disposed adjacent and to extend substantially from the drill central rotational axis; a second cutting portion being disposed further from the drill central rotational axis than said first cutting portion; said first and second cutting portions being configured and disposed to contact and cut a workpiece in a drilling process; a non-cutting portion being disposed between and adjoining said cutting portions; said non-cutting portion being configured and disposed to not contact and not cut a workpiece in a drilling process; said first cutting portion and said non-cutting portion being disposed to meet at a first cutting corner; said non-cutting portion being disposed radially closer to the central rotational axis than said first cutting corner; said first cutting portion and said non-cutting portion at said cutting corner define a cutting angle of ≦90°; and said non-cutting portion has a cross-sectional profile in a plane perpendicular to the central rotational axis which is configured such that for any point on said non-cutting portion, an extended tangent immediately on one side of the point lies on top of another extended tangent immediately on the other side of the point, wherein: said drill bit comprises at least one chip flute portion disposed to extend substantially along the central rotational axis from said second cutting portion, said at least one chip flute portion having a curved cross-sectional profile in a plane perpendicular to the central rotational axis along a circular arc line of a circle having a radius, the length of the radius is such that the circle defined by the radius lies within a free space in a plane perpendicular to the central rotational axis, which free space is defined by said first and second cutting portions and said non-cutting portion, and which free space is enclosed by an outer circle defined by the drill bit circumference, and said non-cutting portion and said second cutting portion merge with each other without interruptions.