A turning insert includes a top surface, an opposite bottom surface and a reference plane located parallel to and between the top surface and the bottom surface. A nose portion has a convex nose cutting edge, a first cutting edge and a second cutting edge. The nose cutting edge connects the first and second cutting edges. The first and second cutting edges form a nose angle () of 71-85 relative to each other. The nose portion includes a third convex cutting edge adjacent to the first cutting edge and a fourth cutting edge adjacent to the third convex cutting edge. The fourth cutting edge forms an angle () of 10-30 relative to a bisector. The distance from at least a portion of the fourth cutting edge to the reference plane increases as the distance from the nose cutting edge increases.

A vibration cutting insert includes a top surface having a rake face and a breaker face, a first side surface, a second side surface, and a bottom surface. In a cross section which includes a bisector of an angle formed between a first ridgeline and a second ridgeline when viewed in a direction from the top surface toward the bottom surface, and which is parallel to the direction from the top surface toward the bottom surface, a rake angle formed between the rake face and a plane parallel to the bottom surface has a positive angle. The angle formed between the first ridgeline and the second ridgeline is an acute angle. The rake face constitutes a cylindrical surface. The breaker face constitutes a flat surface.

A polygonal cutting blade having a circular arc-shaped groove in a hole includes a blade body composed of an upper surface, a lower surface and a plurality of main side surfaces connecting the upper surface and the lower surface. The blade body has a central hole penetrating through the upper surface and the lower surface, and is centrally symmetrical about a central axis of the central hole. At least one set of positioning side surface comprised of adjacent two of the main side surfaces is provided. An inner surface of the central hole has at least one circular arc-shaped groove fitting with a fastening screw for fixing the cutting blade. The circular arc-shaped groove directly faces toward an intersection of the two main side surfaces of the set of positioning side surface. A groove central axis of the circular arc-shaped groove has an offset distance from the central axis.

A disposable cutting insert locking structure includes a shank and a disposable cutting insert. An insert seat is disposed at a front end of the shank. The insert seat has a positioning portion. The positioning portion has a triangular shape. The positioning portion is provided with a screw hole. The disposable cutting insert has a bottom. The bottom is formed with a positioning recess. A through hole is defined in the positioning recess for a screw to be inserted from a top of the disposable cutting insert and screwed to the insert seat.

A cutting insert has cutting edges having the same shape and provided at respective corners of a polygon in rotational symmetry about the center axis of the polygon, is clamped in an upright position to a holder, and has a negative side rake angle on a rake face of a side cutting edge. A side cutting edge is present at an intersection ridge between a polygonal face and an outer peripheral face. The outer peripheral face includes a rake face of the cutting edge and a flank of an end cutting edge of another cutting edge different from the side cutting edge. The flank has a positive slope angle in opposition to a negative side rake angle of the side cutting edge. A breaker groove extending in a front-rear direction is formed in the rake face and cuts into the flank, in such a manner as to divide the rake face.

A cutting insert for a tool for machining a workpiece, comprising a first cutting edge and a first cutting insert bore, wherein the cutting insert has an elongate shape and extends along a cutting insert longitudinal direction, wherein the first cutting insert bore extends along a first bore axis, which runs substantially orthogonally to the cutting insert longitudinal direction, wherein the cutting insert has a laterally protruding elevation, which is arranged on a side of the cutting insert that is oriented transversely to the first bore axis, and wherein on the elevation are arranged a first lateral holder contact surface, an axial holder contact surface and a first horizontal holder contact surface for the bearing contact of the cutting insert against a tool holder, wherein the first lateral holder contact surface runs substantially orthogonally to the first bore axis, and wherein the axial holder contact surface and the first horizontal holder contact surface run substantially orthogonally to the first lateral holder contact surface and transversely to each other.

A round double-sided cutting insert includes an insert peripheral surface that includes a plurality of angularly spaced apart indexing latches protruding therefrom and a plurality of cylindrical insert side abutment surfaces that circumferentially alternate with the plurality of indexing latches. An insert holder has a pocket peripheral surface which includes at least one indexing gap and a plurality of pocket side abutment surfaces that circumferentially alternate with the at least one indexing gap. When the cutting insert is releasably attached to the insert holder, to constitute a fastened position of a cutting tool, each of the plurality of pocket side abutment surfaces abuts a respective insert side abutment surface and each indexing gap has a respective indexing latch located therein.

A rotary cutting tool insert according to one embodiment of the present invention includes: an annular rake face provided with at least one recess portion; and a cutting edge formed at an outer circumference of the rake face, the recess portion having a width of more than or equal to 1.2 mm and less than or equal to 3.0 mm in a circumferential direction of the rake face, a distance between the cutting edge and an end of the recess portion at the outer circumference side of the rake face being more than or equal to 0.1 mm and less than or equal to 0.5 mm. According to the rotary cutting tool insert according to the one embodiment of the present invention, roughness of a processed surface and vibration due to a cutting process can be prevented.

A turning insert has two opposite main surfaces and a peripheral surface which extends therebetween and has N side surfaces, where 2<N<9. The insert has mirror symmetry about a mid-plane and 360/N degree rotational symmetry about a central axis perpendicular to the mid-plane. The insert has two main edges which each have N main cutting edges and N corner cutting edges. Each main cutting edge has two raised edge portions and a lowered edge portion. Each main surface has N main rake surfaces and N corner rake surfaces. Each main surface further has at least N convex island protrusions and N at least partially convex peninsula protrusions, any and all island protrusions associated with a given main rake surface being located between two adjacent peninsula protrusions, each pair of adjacent peninsula protrusions having at least one island protrusion located therebetween.

The invention relates to a cutting tool with a holder, a cutting insert and a screw, wherein the holder has at least one seat with a base, a first side wall and a second side wall, wherein in a plane parallel to the base the first side wall extends in a first direction and the second side wall includes an acute angle (C) with the first side wall, wherein the base has a threaded hole for receiving the screw, wherein the cutting insert has a cut-out for the screw, wherein the cutting insert has a base contact surface, a first positioning surface and a second positioning surface, and wherein in a locked position the base contact surface, the first positioning surface and the second positioning surface of the cutting insert contact the base, the first side wall and the second side wall of the at least one seat, respectively, wherein the second side wall is offset from the threaded hole in the first direction towards a front end of the seat, and in that a screw head of the screw and the cut-out of the cutting insert are provided with complementary conical surfaces, such that when tightening the screw the cutting insert is forced with the first positioning surface and the second positioning surface against the first side wall and the second side wall, respectively.