A twist drill having a shaft with a longitudinal axis, wherein the cutting tool includes a plurality of flutes extending about the longitudinal shaft along a helix angle and a plurality of lands adjacent the flutes. Each land has a cutting edge adjacent a corresponding flute and a margin (i.e. relief surface). A cutting point is adjacent a forward end of the shaft. A first, second and third forward cutting surfaces are adjacent the first, second and third cutting edges, respectively, and extend proximate the cutting point axially rearward for a predetermined length about the longitudinal axis of the shaft. The cutting edges are unequally angularly spaced from each other, and each forward cutting surface has a primary relief angle that are unequal to each other.

A drilling tool includes at least two chip flutes and a chisel edge with a thinned region. The thinned region merges continuously into the chip flutes in such a way that the thinned region forms the end of the respective chip flute in the region of the chisel edge.

A drilling tool includes at least two chip flutes and a chisel edge with a thinned region. The thinned region merges continuously into the chip flutes in such a way that the thinned region forms the end of the respective chip flute in the region of the chisel edge.

In an embodiment, a drill includes a bar-shaped body rotatable around a central axis. The body includes a first surface located at a first end, a second surface intersecting with the first surface on a front side in a rotation direction, and a cutting edge located at an intersection of the first surface and the second surface. The second surface includes a first region located along the cutting edge, and a second region located on a front side in the rotation direction with respect to the first region. The second surface has a concave shape in a cross section orthogonal to the central axis.

A drill has a thinning rake face formed in the front end. An intersection ridgeline between the thinning rake face and the tip flank face is the thinning edge. On the opposite side of the rotation direction, the first and second thinning wall surfaces (6b, 6c) and are formed. Viewed from the front, an intersection angle between the thinning edge (4a) and the first thinning ridgeline is larger than 95. The second thinning ridgeline (L2) is bent to the opposite side of the rotation direction. The thinning edge and the first thinning ridgeline are connected via a concave curve line. The first and second thinning wall surfaces are connected via a concave surface, and a curvature radius of the concave curve line is smaller than a curvature radius of the concave surface.

The modular carrier tool (2), in particular drilling tool, extends along a central longitudinal axis (4) in axial direction (6) and comprises a carrier (8) as well as a tool head (10) that can be reversibly mounted on the front-end of the carrier (8). The carrier (8) has a head retainer (14) for the insertion of the tool head (10) as well as clamping webs (24), which radially delimit the head retainer (14) and also have bearing surfaces (28). The tool head (10) comprises clamping surfaces (35) extending in axial direction as well as underhead bearing surfaces (34). In a mounted state the clamping webs (24) clamp the tool head (10) in radial direction to the clamping surfaces (35) and the underhead bearing surfaces (34) are pressed against the bearing surfaces (28). In order to generate a force component (K) acting in radial direction unto the clamping webs (24), the bearing surfaces (28) as well as the underhead bearing surfaces (34) are tilted in radial direction towards the central longitudinal axis (4) by a tilt angle . This particularly supports the radially exerted clamping force of the elastic clamping webs (24).

A drill configured for drilling ductile materials includes a drill margin with a margin extremity adjacent to a relief surface. The drill includes a drill body and a drill head secured to the drill body via rotational coupling of the drill head on the drill body.

In an embodiment, a drill has an elongated shape and a rotation axis. The drill includes a drilling portion, a shank portion, and a tapered portion. The shank portion includes a first helical flute and a first cutting edge. The tapered portion is located between the drilling portion and the shank portion. The tapered portion includes a second helical flute, a second cutting edge, a chamfered part, and a connection part. The chamfered part is getting smaller gradually as moving toward the first end side. The connection part has a curved surface and connects the second cutting edge and the drilling portion. A ratio of w/L is 0.0015-0.5 where L is a length of the second cutting edge in a front view of the first end, and w is a width of an outer peripheral end of the chamfered part in a direction parallel to the rotation axis.

A drill includes a cutting edge. The cutting edge has a point angle which is continuously decreased from a center-position point angle A (herein, 0<A<180) at a center position to a maximum-diameter-position point angle of 0 at a maximum diameter position. The cutting edge has a relief angle which is continuously decreased from the center position to the maximum diameter position. The cutting edge of the drill has a relief angle at the maximum diameter position. Hence, the cutting edge also serves as a cutting edge for reaming. The ridgeline and relief face of the cutting edge have no corner, thereby providing good wear resistance.

A drill (1) based on an embodiment of the present invention is equipped with: a first chip discharge flute that is provided on an outer periphery of a drill body and spirally extends around a rotational axis from a first cutting edge toward a rear end of the drill body; a second chip discharge flute that is provided on the outer periphery of the drill body and spirally extends around the rotational axis from a second cutting edge toward the rear end of the drill body; and an auxiliary flute that is provided on the outer periphery of the drill body and extends along the second chip discharge flute on a front side in a rotating direction of the rotational axis, wherein a rear end of the second chip discharge flute extends further toward the rear end of the drill body than the first chip discharge flute.