The drill head (2) extends along a rotational axis (24) in the axial direction (22) and has a central area (6) on the front with first main cutting edges (26), an intermediate area (8) connecting thereto, and an outer area (10) in turn connecting thereto with second main cutting edges (30). The intermediate area (8) in this case expands in the axial direction (22) toward the outer area (10) and in particular forms an expanding conical shell. A centering effect is hereby achieved via the intermediate area (8).

A drill comprising: a drill main body; a chip discharge flute; and a tip cutting edge. The tip cutting edge includes: a first tip cutting edge which extends toward the axially posterior end as it goes toward the outside in a radial direction; and a second tip cutting edge which is disposed outside the first tip cutting edge in the radial direction. The second tip cutting edge extends toward the tip in the axis direction as it goes toward the outside in the radial direction or extends to be perpendicular to the axis. The radially inner end of the second tip cutting edge is disposed on the axially posterior end with respect to the radially outer end of the first tip cutting edge. The radially outer end of the second tip cutting edge is disposed on a virtual extension line of the first tip cutting edge.

Provided is a drill having a flat-shaped drill tip and excellent in cutting edge strength and chip removability. The drill includes: a cutting edge extending in a direction at an angle α of not less than 85° and not more than 90° with respect to a drill axis (line O-O); a flank face contiguous to the cutting edge and having a clearance angle β of not less than 5° and not more than 10° with respect to the drill axis (line O-O); and a rake face located opposite to the flank face across the cutting edge, the cutting edge includes a recess receding in a direction parallel to the drill axis (line O-O), and the rake face includes a front clearance formed at a side of an outer periphery of the drill.

A cutting head rotatable about a central axis, comprising a tip portion and an intermediate portion. The tip portion has an axially forwardmost tip point contained in the central axis and three axially forward facing front surfaces forming three chisel edges extending axially rearwardly away from the tip point, each front surface having a radially extending cutting edge comprising a secondary cutting-edge portion extending radially outwardly from one of the chisel edges, and a primary cutting-edge portion extending radially outwardly therefrom. Each primary cutting-edge portion is contained in an imaginary annular ring surface having an annular ring width spanning at least radially inner and outer end points thereof. In a front-end view of the cutting head, each primary cutting-edge portion is concave, and radial planes intersect the imaginary annular surface to form imaginary rectilinear lines, each having a length equal to the annular ring width.

A drill includes a bar-shaped drill body, a major cutting edge which is located at a front end of the drill body and has a straight-line region in a front view, a rake surface located along the major cutting edge, and a chip discharge flute being extended spirally around a rotation axis of the drill body in a direction from the rake surface toward a rear end of the drill body. The rake surface has a flat region located along the straight-line region.

In this drill, a main cutting edge is formed on a tip-side ridge portion of a chip discharge flute (6) formed on an outer periphery of a tip portion of a drill body, a thinning edge is formed on a tip-side ridge portion of a thinning portion having a concave groove shape formed on a tip inner peripheral portion of the chip discharge flute, when viewed from a twist direction of the chip discharge flute, a radius of an the chip discharge flute inscribed circle is in a range of 0.3×D2 to 0.7×D2 with respect to a diameter D2 of a second circle; in the thinning portion, a radius (R2) of a thinning inscribed circle (C6) is in a range of 0.3×d to 0.7×d with respect to a core diameter (d) when viewed in a thinning direction.

Disclosed are a drill and an insert for a drill having improved centering capability and cutting performance. In the drill of the present disclosure, central relief surfaces of cutting parts are processed as flat relief surfaces, and outer circumferential relief surfaces continuing from the center part to the outer circumferential surface of the drill are processed as curved relief surfaces, thereby enhancing the centering capability of the drill and minimizing the generation of drill vibration and burrs. In addition, in the drill of the present disclosure, the outer relief surfaces of the drill in contact with a hole to be drilled are processed such that an angle between the tangential lines of the outer relief surfaces is constant regardless of the size of the outer diameter of the drill, thereby achieving consistent performance of the drill despite change in the outer diameter of the drill.

Provided herein is a drill having less possibility of cracks in an inner periphery of a drilled workpiece and deformation of a workpiece upon penetrating with a drill, as well as delamination. A drill according to the present invention comprises two cutting blades which are formed symmetrical about an axis of rotation, wherein each of the cutting blades has a main cutting blade formed from a drill tip toward a peripheral side of the drill to become a shape with curves, a thinning cutting blade in a shape with curves formed in closer to the drill tip than the main cutting blade, and an U-shaped cutting blade in a shape with curves formed in closer to the periphery of the drill than the thinning cutting blade.

The invention relates to a rotary cutting tool (1), such as a drill (2) or a reamer (3), extending longitudinally along an axis (4) and comprising at least one main cutting edge (5) so that when the tool (1) is rotated about the axis (4), the tool (1) advances axially to perform a cutting operation on a material.

According to the invention, the tool (1) comprises means for braking (7) the axial advance of the tool (1) during the cutting operation.

The combination tool (2), in particular a drilling/chamfering tool, comprises a drill (6) extending in the longitudinal direction (4) with a clamping sleeve (8), which is designed to receive the drill (6) and fasten the drill (6) at a variable length and which has a holding seat (38) for a cutting insert (12). The drill (6) comprises a cutting region (22) provided with grooves (14), wherein the grooves (14) extend helically and are formed between two grooves (14) drill backs (18). At least one of the drill backs (18) is partially flattened to form an adjustment surface (16) for the cutting insert (12), wherein the adjustment surface (16) extends helically. As a result, a length adjustment over a large length range is made possible independently of the twist angle (γ).