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.

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 head is rotated about a center axis. The drill head includes: a mounting surface that is an end face in a direction of the center axis; a tip surface that is an opposite surface to the mounting surface in the direction of the center axis; an outer peripheral surface continuous to the mounting surface and the tip surface; a cutting edge extending from the outer peripheral surface toward the center axis in the tip surface; a flute that is formed on the outer peripheral surface and extends spirally around the center axis from the tip surface to the mounting surface; and a thinning surface continuous to the tip surface and the flute. The tip surface includes: a first flank surface continuous to the cutting edge; and a second flank surface located on a side opposite to the first flank surface with the flute interposed therebetween.

A method for manufacturing a sintered component includes a compaction step of press-compacting a starting powder containing a metal powder to form a compact; a drilling step of forming a hole in the compact with a drill to form a thin portion where the thickness between an inner circumferential surface of the hole and an outer surface of the compact is smaller than the diameter of the hole; and a sintering step of sintering the compact after the drilling step. The drilling step is performed while the outer surface of the compact is pressed in a region extending over the entire length of the hole in an axial direction. The width of the region where the outer surface of the compact is pressed is from 1/3 times to twice the diameter of the hole.

A tool for producing an internal thread in a workpiece pilot hole having a thread major diameter and a thread minor diameter, which tool has a thread-forming section, by which an internal thread profile can be produced in a pilot hole wall. The internal thread profile having the thread major diameter and a thread inner diameter. The tool has a drilling section, by which the thread inner diameter of the internal thread profile can be expanded to the thread minor diameter by machining. At least one, in particular exactly one chip groove is associated with the drilling section of the tool, by which chip groove the chips produced as the thread inner diameter is expanded to the thread minor diameter can be transported away.

A cutting tool has a rake face and a flank face. The flank face is provided with a coolant supply hole. A ridgeline between the rake face and the flank face forms a cutting edge. An outer shape of the coolant supply hole in a cross section orthogonal to an axis includes a first portion facing the cutting edge, and a second portion opposite to the cutting edge when viewed from the first portion. The first portion has a concave portion extending toward the second portion. The concave portion is defined by a first side portion and a second side portion facing each other, and a bottom continuous with both the first side portion and the second side portion. In the cross section, an angle formed by a tangent of the first side portion and a tangent of the second side portion is not more than 160.

A drill of the present invention includes: a drill main body; a plurality of convex-arc cutting edges which are formed on a tip side of the drill main body from an outer periphery of the drill main body to a chisel edge provided near to a rotational axis; second faces which are each formed in an approximately band shape and are each formed along each of the convex-arc cutting edges on a back side of the convex-arc cutting edge in the rotational direction; third faces which are each formed to be continuous with a back side of each of the second faces in the rotational direction; and fourth faces which are each formed to be continuous with a back side of each of the third faces in the rotational direction.

The drill (1) is provided with a drill body (2) having a rotation center axis (O), two cutting edges (3) provided on the tip side of the drill body (2), and chip evacuation flutes (10) provided behind the two cutting edges (3) in the direction of rotation of the drill (1) from the two cutting edges, the drill tip angle () being from 170 to 190, the web thickness (d) being from 0.10 to 0.25 times the drill diameter (D), the opening angle () of the chip evacuation flutes (10) being from 85 to 110, and the drill (1) comprising a curve having a radius of curvature that gradually decreases from the cutting edge side wall surface (14) to the heel side wall surface (15) of the chip evacuation flutes (10) in a cross-section at a position where the chip evacuation flutes (10) are present.

A method for designing a cutting edge of a cutting element configured for removing material from a workpiece to leave therein a desired end profile (B22,B24,B26). The method comprises the steps of modeling a desired end profile (B22,B24,B26) of the workpiece, the profile having a longitudinal axis and being defined by a bottom surface (B12), a side surface (B16) and an adjustment surface (B14) extending therebetween; defining a lead profile plane (RP.sub.L) and an trail profile plane (RP.sub.T) spaced therefrom, each of the planes being oriented perpendicular to the longitudinal axis; determining a profile contour defined by the intersection line between the end profile (B22,B24,B26) and the lead profile plane (RP.sub.L). The contour profile includes a bottom contour, an adjoining contour and a side contour defined as the intersection lines between the lead profile plane (RP.sub.L) and the bottom surface (B12), the adjustment surface (B14) and the side surface (B16) respectively; designing a rake surface and a relief surface, the intersection line between which defines a cutting edge lying in the adjoining surface (B14) and spanning between the lead profile plane (RP.sub.L) and the trail profile plane (RP.sub.T). The cutting edge is designed such that in any reference plane (RP; FIG. 6A) oriented perpendicularly to the cutting edge, the intersection between each of the rake surface and the relief surface with the reference plane (RP) defines a respective rake line (RK; FIG. 7) and relief line (RF; FIG. 7), the angle (.sub.B) between the lines RK,RF) being equal to or smaller than a similar angle (.sub.B) taken along each of a plurality of similar reference planes (RP) disposed between the reference plane (RP.sub.n) and the lead profile plane (RP.sub.L).

A fluted drill comprises, in axial sequence, a body portion, and a cutting portion. The cutting portion comprises two or more cutting edges, with each cutting edge extending from a distal end of the cutting portion, along the cutting portion towards the body portion, to the body portion.

Each cutting edge has a first rake angle at the distal end of the cutting portion, progressively increasing to a third rake angle at a proximal end of the cutting portion. Each cutting edge has a first uncut chip thickness at the distal end of the cutting portion, progressively decreasing to a third uncut chip thickness at the proximal end of the cutting portion.