According to one implementation, a drill includes the first cutting edges, the second cutting edges and a deflection reducer. The first cutting edges drill a prepared hole to a workpiece. The first cutting edges are formed in a tip side of the drill. The first point angle and each first relief angle of the first cutting edges continuously or intermittently decrease from the tip side toward a rear end side of the drill. The second cutting edges finish the prepared hole. The second cutting edges are formed at positions away in the rear end side from the first cutting edges. The second cutting edges have the second relief angles at a maximum diameter position. The deflection reducer reduces deflection of the second cutting edges. The deflection reducer is formed between the first cutting edges and the second cutting edges. The deflection reducer is inserted into the prepared hole.

One example of the present disclosure relates to a coupon. The coupon includes a first surface with a first circular channel and a second surface opposite and parallel to the first surface. The second surface is spaced a distance D0 from the first surface and includes a second circular channel concentric with the first circular channel. The coupon also includes a toroidal portion between the first circular channel and the second circular channel. The toroidal portion includes a rectangular sectional portion.

Methods of forming a drill bit or boring tool having a cutting edge that includes a pair of generally smooth curvilinear shaped portions that are positioned near the radial outer portions of the cutting edge and connected to one another by a pair of generally linear portions that traverse a longitudinal centerline of the tool.

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.

A drill reamer (20) comprises an elongate body (21) disposed about a longitudinal axis. The elongate body comprises flutes (22a-22d) having separate hard cutting sections (27a, 28a, 28a, 28b, 28b) and a soft cutting section (24a, 24b). The soft cutting section is formed of a material such as carbide having a hardness that is less than that of the hard cutting sections, which may be formed of polycrystalline diamond. At least one first hard cutting section (27a) is axially displaced relative to at least one second hard cutting section (28a, 28a). The reamer has a tip cutting edge (23a, 23c) and tapered cutting edge portions (24a-24d) disposed at an acute angle relative to the longitudinal axis.

A flat drill having a handle, and a flat blade formed in the front portion of the handle part. A front portion of the flat blade extends inwardly from the two sides, forming first and second shoulder. The two shoulders continuing to extend and taper inward and upward, forming two tapered sections respectively, a first tapered section and a second tapered section, and having a pointed top. A first groove is formed on a blade part of the first shoulder toward the inside of the flat blade part. The inner edge of the first groove is inclined downward towards outside direction of the first shoulder, forming an angle of greater than 0 degree with respect to a horizontal line of the flat drill.

A single-lip drill including at least one cutting edge on a drill head has a face which is concave along at least 75 percent of the width thereof and substantially along the entire length thereof, all the way to, and inclusive of, the cutting edge.

A drill includes a cutting section having a cylindrical shape and configured to be rotated about a rotation axis. The cutting section includes a first cutting section and a second cutting section, at a front end portion thereof, a first flute continuous with the first cutting section and extending helically around the rotation axis toward a rear end of the cutting section, and a second flute continuous with the second cutting section and extending helically around the rotation axis toward the rear end of the cutting section. The first cutting section includes a first inner cutting edge and a first outer cutting edge positioned closer to the outer peripheral surface than the first inner cutting edge and gradually inclined to the rear end of the cutting section toward the outer peripheral surface. The first inner cutting edge is positioned closer to the rear end of the cutting section than the inner end of the first outer cutting edge.

A drill bit or boring tool having cutting edge that includes a pair of generally smooth curvilinear shaped portions that are positioned near the radial outer portions of the cutting edge and connected to one another by a pair of generally linear portions that traverse the longitudinal centerline of the tool.

Disclosed is a cutting tool, including: a cutting edge including a coating from a rake face to a flank face, and has a relief angle of not less than 15 degrees, a material of the coating having a higher wear resistance than a base material of the cutting edge, and during cutting of a work, an edge of the coating on the rake face at a top of the cutting edge is worn by friction with the work; with a progress of a wear inward in a radial direction, an edge of the coating on the flank face at the top of the cutting edge is removed by friction with the work to expose the base material thereunder; and the exposed base material is worn by friction with the work to retract the flank face inward in the radial direction.