An indexable cutting insert has opposing upper and lower end surfaces, and a peripheral surface including three side surfaces circumferentially alternating with three corner surfaces. The three side surfaces define an imaginary triangle and an imaginary hexagon. Each corner surface intersects the upper end surface to form an upper corner peripheral edge having a primary cutting edge. In a top view, each triangle side traverses two upper corner peripheral edges, imaginary lines tangential to the end points of each primary cutting edge are either collinear or form an obtuse angle greater than 175 degrees, each primary cutting edge has a primary length greater than half the hexagon side length, and at least one triangle side traverses each primary cutting edge. The insert is removably secured in a rotary cutting tool such that one of the upper corner peripheral edges contains an axially forwardmost point of the insert's upper peripheral edge.

This cutting insert is provided with a lower surface of polygonal shape including side parts and a pair of corner parts, an upper surface, a lateral surface situated between the lower surface and the upper surface, a pair of corner cutting edges located at the pair of corners, and a main cutting edge located in a side portion. The main cutting edge is upwardly convex in shape, and in side view includes an upwardly convex curving portion, and a pair of linear portions respectively extending toward the pair of corner cutting edges from the curving portion. The top portion of the curving portion is positioned more toward the one of the corner cutting edges which, of the pair of corner cutting edges, is that contiguous to a working surface of a work material during cutting of the work material.

A cutting insert for a milling tool, having a first side, a second side which is identical to the first side and a circumferential surface which extends between the first and the second sides, with a bore which extends along a bore axis. The cutting insert is 120 rotationally symmetrical with respect to the bore axis and comprises on each of the first side and the second side three identically formed cutting regions, respectively, which are situated at a transition between the first side and the circumferential surface or at a transition between the second side and the circumferential surface, respectively Each of the in total six cutting regions comprises a first rectilinear cutting edge, a second rectilinear cutting edge, and a third arcuate cutting edge, wherein a first end of the first cutting edge is connected to a first end of the third cutting edge, and a first end of the second cutting edge is connected to a second end of the third cutting edge, wherein the first and the second cutting edges are of same length. The cutting insert comprises on the first side a first contact surface which extends orthogonally to the bore axis and lies in a first contact plane, and on the second side comprises a second contact surface which extends orthogonally to the bore axis and lies in a second contact plane, and wherein each of the first cutting edges are connected at their second ends, which are located opposite the first ends, to one of a total of six arcuate edges, a vertex of which is located between the first and the second contact planes.

A cutting insert includes first and second polygonal surfaces and a plurality of side surfaces. A corner edge that has a corner rake surface on the first polygonal surface is formed at a first corner portion, and a main cutting edge is formed from the corner edge to a second corner portion. The main cutting edge includes, at least on a corner edge side, a rake angle gradual increase region where a rake angle of a main rake surface gradually increases to a positive angle side as going from a first end portion of the corner edge toward a second corner portion side.

Provided is a cutting insert capable of suppressing edge fracture when a work having high hardness is machined. A cutting insert includes two end surfaces having a plurality of corner parts and opposed to each other, a peripheral side surface extending between the two end surfaces, and a cutting edge formed at an intersecting edge between at least one of the two end surfaces and the peripheral side surface. The cutting edge has at least a first corner edge, a second corner edge, a major cutting edge, and an end cutting edge. The end cutting edge has a circular-arc shape, which projects outward, as viewed from the side of the end surface. The end cutting edge has a width which is from 15% to 50% of the width of the cutting insert. The end cutting edge has an arc radius which is from to 1/1 of the width of the cutting insert.

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).

This cutting insert is provided with a lower surface of polygonal shape including side parts and a pair of corner parts, an upper surface, a lateral surface situated between the lower surface and the upper surface, a pair of corner cutting edges located at the pair of corners, and a main cutting edge located in a side portion. The main cutting edge is upwardly convex in shape, and in side view includes an upwardly convex curving portion, and a pair of linear portions respectively extending toward the pair of corner cutting edges from the curving portion. The top portion of the curving portion is positioned more toward the one of the corner cutting edges which, of the pair of corner cutting edges, is that contiguous to a working surface of a work material during cutting of the work material.

Milling inserts having surfaces designed for supporting the insert relative to a milling cutter body, and a milling tool are provided. The milling insert has a first end surface, a second end surface, and a side surface extending between the first end surface and the second end surface At least one cutting edge is defined by an intersection of at least one of the first end surface and the second end surface with the side surface. The at least one cutting edge includes a radiused component having a first end and a second end and first and second components at the first and the second ends of the radiused component, respectively. The first and second components are less curved than the radiused component. The side surface has at least one substantially V-shaped valley formed by first and second support surfaces.

To reduce burrs that may be formed at a corner portion of a machined surface in a face milling process, there is provided a cutting insert that does not tend to form burrs. A milling cutting insert includes cutting edges provided as ridges each defined by an upper or lower face and a side face that intersect each other, the cutting edges including a flat cutting edge. The cutting edge include a major cutting edge provided between adjacent ones of corner portions, the flat cutting edge provided at the corner portion, and a minor cutting edge provided between the major cutting edge and the flat cutting edge. A surface roughness of a side face that is continuous with the major cutting edge is higher than a surface roughness of a side face that is continuous with the minor cutting edge.

A double-sided milling cutting insert has a first cutting edge disposed at an intersection of a top side and a side surface and a second cutting edge disposed at an intersection of a bottom side and the side surface. Each of the first and second cutting edges contains three cutting edge portions which are useable by indexing. The cutting edge portions each have a cutting corner, a main cutting edge adjacent to one side of the cutting corner, and a wiper edge adjacent to the other side of the cutting corner. The main cutting edge and the wiper edge are each inclined towards a reference plane with increasing distance from the cutting corner such that the first and second cutting edges have the largest distance to the reference plane in the regions of the cutting corners. The side surface has main clearance surfaces, secondary clearance surfaces, and curved corner surfaces.