A rotary tool may include a base. The base may be extended from a first end to a second end. The base may include a first part and a second part. The first part may include the first end. The second part may have a larger outer diameter than the first part. The first part may include a first flute. The second part may include a second flute. In a first cross section of the first part, the first flute may include a first bottom part. A center of a first imaginary circle overlapping with the first bottom part may be located outside a circumscribed circle of the first part. In a second cross section of the second part, the second flute may include a second bottom part. A center of the second imaginary circle overlapping with the second bottom part may be located inside a circumscribed circle of the second part.

In this small-diameter drill bit, two cutting blades having main cutting blades, of which a difference between lengths are 0.04 mm or less, are formed on a tip of a double-margin drill bit body having a diameter of 2 mm or less and a margin length/diameter ratio of 3 or more. Two tip flank faces are formed such that a first extension line extending from a linear first intersecting ridgeline between a first tip flank face and a second tip flank face of one of the flank faces to the linear first intersecting ridgeline of the other flank face is located on a side in the drill bit rotation direction with respect to the other linear first intersecting ridgeline. A distance between the first extension line and the linear first intersecting ridgeline is in a range of 0.04 mm-0.08 mm.

A drill may be extended from a first end to a second end and may include a cutting part. The cutting part may include a cutting edge, a flute, an end surface and a connection surface. The flute may be extended from the cutting edge toward the second end. The end surface may be located closer to the second end than the flute. The connection surface may be located between the flute and the end surface. The connection surface may include a first portion, and a second portion located closer to an outer periphery of the cutting part than the first portion. A length in the direction along the rotation axis on the second portion may be smaller than a length in the direction along the rotation axis on the first portion in a side view orthogonal to the rotation axis.

A drill includes a leading end portion. The leading end portion is flat and has at least two cutting blades extending from a rotation center toward outside in a radial direction. The each cutting blade includes an arc-shaped portion. An inside linear portion is formed in a linear shape and connects to one end of the arc-shaped portion on the rotation center side. An outside linear portion is formed in a linear shape and connects to another end of the arc-shaped portion on an opposite side to the one end. The arc-shaped portion has a cutting edge provided with an arc-shaped portion chamfered surface. The inside linear portion and the outside linear portion each has a cutting edge provided with a linear portion chamfered surface. A drill axis direction width of the arc-shaped portion chamfered surface is smaller than a drill axis direction width of the linear portion chamfered surface.

A drill in which: a chip discharge groove is formed in an outer periphery of an edge portion serving as a leading end side portion of a drill body; and a cutting edge is formed in an intersecting edge between a rake surface of a leading end side region and a leading end flank of the edge portion, the drill comprising a margin portion, a shoulder portion and a web thinning portion, wherein: the cutting edge comprises, in order from a rotation center, a first cutting edge portion, a second cutting edge portion, a shoulder cutting edge portion, and a margin cutting edge portion; the honing width gradually decreases from the boundary P1 toward the position P2; and the conditions represented by expression (1): honing width of second cutting edge portion≤R1 and expression (2): 2.0<R1/R2<5.0 are satisfied.

A small-diameter drill in which is a double margin having a diameter of 2 mm or less and a ratio of a margin length to a diameter of 3 or more, in which the margin length L in an axial direction from an outer peripheral end of a cutting edge to the rear ends of first and second margin parts and a ratio L/D to a diameter D are 3 or more, in which at least a surface of a chip discharge groove is provided with a hard coating made of nitride, in which a surface of the hard coating in the chip discharge groove has skewness (Ssk) defined in ISO25178 of less than 0, and in which the number of droplets having an equivalent circle diameter of 1.0 μm or more is 5 or less per 100 μm.sup.2 in cross-section observation of the hard coating.

A rotary cutting tool includes a tool body including a chip flute portion having a plurality of helical chip flutes separated by lobes. In one aspect, a tunable vibration absorber assembly is disposed within a cavity formed in the chip flute portion. In another aspect, the tunable vibration absorber assembly is disposed within a cavity of a replaceable cutting head. In each aspect, the tunable vibration absorber assembly includes one or more tunable absorber masses, a resilient material between the one or more absorber masses and the cavity, and one or more connecting members for preventing relative angular displacement of the one or more tunable absorber masses. The one or more tunable absorber masses are suspended only by the resilient material, thereby enabling the tunable vibration absorber assembly to be tuned to a desired frequency for suppressing torsional vibration of the rotary cutting tool during a cutting operation.

A rotary cutting tool includes a tool body including a chip flute portion having a plurality of helical chip flutes separated by lobes. In one aspect, a tunable vibration absorber assembly is disposed within a cavity formed in the chip flute portion. In another aspect, the tunable vibration absorber assembly is disposed within a cavity of a replaceable cutting head. In each aspect, the tunable vibration absorber assembly includes at least two tunable absorber masses, a resilient material between the one or more absorber masses and the cavity, and one or more connecting members for preventing relative angular displacement of the one or more tunable absorber masses. The at least two tunable absorber masses are suspended only by the resilient material, thereby enabling the tunable vibration absorber assembly to be tuned to a desired frequency for suppressing torsional vibration of the rotary cutting tool during a cutting operation.

A rotary cutting tool includes a replaceable cutting insert, a pocket portion for holding the cutting insert, and a chip flute portion having a plurality of helical flutes. An internal coolant passage is formed in the chip flute portion and has both a twisted geometry and a “see-through” central portion. The internal coolant passage is polygonal in cross-sectional shape having a number of cusps equal to the number of flutes. The internal coolant passage greatly increases coolant flow area, while maintaining the stiffness and rigidity of the cutting tool. A method includes forming the internal coolant passage using additive manufacturing such that the internal coolant passage has a “see-through” central portion and a twisted geometry.

Cutting tool for the rotary machining of workpieces, in particular a twist drill, with a cutting tip which has at least one main cutting edge and at least one free surface (24), wherein a flank face adjoins the main cutting edge radially to the outside, and wherein a flank angle of the flank face increases in a radially outward direction.