A metal drilling tool comprising includes a middle axis, a front side and an opposite end, with at least two cutting edges arranged in a region of the front side, a first free surface being associated with each cutting edge. The at least two cutting edges lie on an imaginary first conical surface arranged concentrically in relation to the middle axis, with a first conical angle that opens up towards the opposite end and reaches a maximum of 180. A centering section includes at least three edges, at least three side surfaces and an imaginary base surface. At least two of the edges lie on an imaginary second conical surface which is arranged concentrically in relation to the middle axis and has a second conical angle that opens up towards the opposite end. The second conical angle is smaller than the first conical angle, such that the imaginary second conical surface, seen from the opposite end, projects opposite the front surface.

A cutting tool and method of manufacturing a tool including determining desired flowrates to cutting edges. The method includes calculating pressure drop and passage dimensions for each of an nth-number of passages to the cutting edges based on I.sub.n=(P.sub.n*A.sub.n.sup.n)/(.sub.n*L.sub.n), wherein I.sub.n is nth-passage flow rate, P.sub.n is nth-passage pressure drop, A.sub.n.sup.n is nth-passage cross-sectional area raised to a power n, the power n being equal to 1 or 0.5, .sub.n is nth-passage resistivity, and L.sub.n is nth-passage length. The method includes forming the nth-passages in the tool open to each cutting edge based on the nth-passage dimensions.

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 cutting head rotatable about a first axis, has a cap portion and a rigid mounting protuberance joined thereto. The cap portion has a plurality of cutting portions circumferentially alternating with a plurality of head chip flutes, and a head base surface facing in an axial rearward direction. The mounting protuberance exhibits rotational symmetry about the first axis, extends axially rearwardly from the head base surface, and has a plurality of circumferentially spaced apart convex clamping surfaces. The plurality of cutting portions define a cutting diameter, the plurality of head chip flutes are inscribed by an imaginary first circle having a first diameter, and the plurality of clamping surfaces are circumscribed by an imaginary second circle having a second diameter. The first diameter is greater than the second diameter, and the second diameter is less than forty percent of the cutting diameter.

Drills and methods of removing material using drills are disclosed. Drills may include a plurality of lands that extend to a cutting edge, where adjacent lands are separated by flutes comprising a base contour arranged in a generally helical configuration along a centerline axis of a drill body. The drill also includes a plurality of contoured drill points each having a linear portion that extends towards an outer diameter of the drill body, and an arcuate portion that extends from the linear portion and towards a chisel of the drill body. The drill further includes a plurality of gash contours positioned within the plurality of flutes. The gash contours extend from the chisel of the drill body, and the gash contours are oblique to the base contours of the flutes.

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 drill bit includes a cutting head and a bit body. The cutting head has a tip and cutting parts. The bit body is connected to the cutting head and has a longitudinal axis extending through the tip. The bit body has chip discharge flutes. The cutting parts are disposed at different angular positions around the longitudinal axis. Each cutting part is concaved inwardly and bounds one of the chip discharge flutes. Each of the cutting parts includes a rake face that has a corner edge adjacent to a respective one of the chip discharge flutes. When a bottom of the cutting head is viewed in a direction parallel to the longitudinal axis of the bit body, the corner edge has an obtuse included angle.

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 drill includes a shank and a body having an outer peripheral surface with a certain outer diameter and a distal end tapered surface of a certain distal end angle. The drill includes a pilot shaft portion projecting from the distal end tapered surface of the body and having a diameter smaller than the body and having an outer peripheral surface of a certain outer diameter. The drill further includes an odd number of twisted grooves extending from the outer peripheral surface of the body to the outer peripheral surface of the pilot shaft portion at a certain twisted angle, an odd number of main cutting edges formed on the distal end tapered surface of the body by forming of the twisted grooves, and an odd number of auxiliary cutting edges formed on the distal end tapered surface of the pilot shaft portion by forming of the twisted grooves.

A three-flute drill includes: three chip discharge flutes; and three cutting edges each having concavely-curved and convexly-curved cutting edge portions, an axially perpendicular cross-sectional view orthogonal to an axial center having first convex and concave curves respectively corresponding to the convexly-curved and concavely-curved cutting edge portions intersecting each other, in the axially perpendicular cross-sectional view, a concave amount of the first concave curve being within a range of 0.01D to 0.05D in terms of a drill cutting diameter relative to a reference line connecting an outer circumferential point, at which a drill outer circumferential portion intersects with the first convex curve, and the axial center, and in the axially perpendicular cross-sectional view, a rake chamfer width being a distance from an intersection between a straight line through the intersection and orthogonal to the reference line and the reference line, to the outer circumferential point, and being within 0.005D to 0.06D.