A cutting insert of the present invention comprises: an upper surface and a lower surface; first and second lateral surfaces; first and second cutting edge parts; and corner cutting edges, wherein the first cutting edge part includes: a first main cutting edge for forming one end at a portion spaced farthest away from the corner cutting edge; a first sub-cutting edge connected to the corner cutting edge; and a first auxiliary cutting edge for connecting the first main cutting edge and the first sub-cutting edge so as to form a step between the same, and the first sub-cutting edge and the corner cutting edge form one straight line when viewed toward the first lateral surface, and are inclined upward in the direction opposite to the direction toward the lower surface while gradually going in the direction toward the second cutting edge part.

In an end mill, eight peripheral cutting edges having a helical shape and g a larger outer diameter than that of a shaft portion are in a cutting portion in a circumferential direction. For one peripheral cutting edge of the eight peripheral cutting edges, when a cut length of the peripheral cutting edge along an axial direction is L, a twist angle of the peripheral cutting edge is , and a circumferential distance at a lower end of the peripheral cutting edge between the peripheral cutting edge and another peripheral cutting edge adjacent to a tool rotation direction rear side of the peripheral cutting edge is a, n expressed by the following equation is approximately 1 for all of the eight peripheral cutting edges in at least a half region of the cut length from the lower end of the peripheral cutting edge.

n=(Ltan )/(2a)

The rotary cutting tool of the invention has helicoidal peripheral cutting edges with a wavy profile.

A cutting tool includes: a body extending along a longitudinal axis between a leading and trailing ends, the body having a clamping region disposed at or about the trailing end and a cutting region which extends toward the clamping region from the leading end of the body; a plurality of flutes defined in the body, each extending from the leading end toward the coupling portion; a plurality of peripheral cutting edges, each extending from the leading end toward the coupling portion along a corresponding flute of the plurality of flutes; and a plurality of end cutting edges disposed at the leading end, each end cutting edge extending from at or near the longitudinal axis outward along a corresponding flute. At least one end cutting edge is defined, in-part, by a plurality of rake faces which each extend from a corresponding portion of the one cutting edge into the corresponding flute.

An indexable rotary cutting tool and insert is capable of performing a high-accuracy cutting process with high efficiency. A twist angle of an outer peripheral cutting edge of the tool has a positive value, an axial rake angle of the cutting edge of a corner R of the tool at a boundary point between the cutting edge of the corner R and the outer peripheral cutting edge has a positive value, the axial rake angle of the cutting edge of the corner R at a reference point has a negative value, and the radial rake angle at least between the boundary point and the reference point in an entire edge length region of the cutting edge of the corner R has a negative value. The radial rake angle at the reference point is smaller than the radial rake angle at the boundary point.

A method of milling a profile of a railway rail comprises: rotating a milling cutter including a plurality of face mounted cutting inserts mounted about a periphery thereof, milling a railway rail with cutting edges of the cutting inserts rotating in a predetermined plane corresponding to at least a portion of a desired rail profile while controlling the depth of cut of the cutting inserts; traversing the railway rail with the milling cutter while milling the railway rail and controlling the speed of traverse of the milling cutter along the railway rail.

A mirror finishing method for mirror-finishing a workpiece includes: a step of performing a first machining operation with a first tool which has a cylindrical portion made of polycrystalline diamond or cubic boron nitride at the tip of a shank thereof and further has a cutting edge formed by forming a linear groove on the cylindrical portion; and a step of, after the first machining operation has been performed, performing a second machining operation with a second tool which has a cylindrical portion made of polycrystalline diamond or cubic boron nitride at the tip of a shank thereof with no cutting edge on the cylindrical portion.

In an end mill body made of ceramic, a corner R rake face is formed in such a manner as to contain a point B and at least a region B, not a region A located on a side toward an end cutting edge. In other words, a first end portion of a cutting edge on a peripheral edge portion of the corner R rake face is formed on a peripheral edge of the region B of a corner R cutting edge, and a second end portion of the cutting edge reaches at least the point B. As a result, partial breakage of the corner R cutting edge is unlikely to occur in the course of cutting. That is, since the corner R rake face is formed in such a manner as to start from the first end portion located apart from a point A, which is the intersection of the end cutting edge and the corner R cutting edge, and such that the second end portion reaches the point B, a large cutting load is unlikely to be imposed on the starting point of the corner R rake face. Therefore, the corner R cutting edge is unlikely to be chipped.

An end mill includes a bar-shaped body, a cutting edge, a gash, a first flute, and a second flute. The body extends from a first end to a second end along a rotation axis. The cutting edge is located at a side of the first end of the body. The gash is located adjacent to the cutting edge. The first flute surrounds the gash and spirally extends from the gash toward the second end. The second flute surrounds the first flute and spirally extends from the first flute toward the second end. A depth of the first flute is greater than a depth of the second flute in a cross section orthogonal to the rotation axis.

The present invention provides an end mill including: a shaft-shaped end mill main body; a chip discharge groove extending from a leading end to a trailing end in an axial direction of the end mill main body; a bottom blade which is provided at a leading end portion in the axial direction of the end mill main body and has a spherical shape in which a rotation locus around the axis has a center on the axis; and an outer peripheral blade which is provided along the chip discharge groove, and in which a rotation locus around the axis is convex outward. A curvature radius of the rotation locus of the outer peripheral blade is larger than a curvature radius of the rotation locus of the bottom blade. A twist angle of the outer peripheral blade is 20 or more.