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.

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 cutting insert includes an upper surface, a lower surface, a side surface, and an upper cutting edge. The upper cutting edge includes a major cutting edge having an outwardly projecting curvilinear shape, and a minor cutting edge having a straight line shape and being continuous with the major cutting edge. The side surface includes a continuous inclined surface with the major cutting edge and is inclined outward from the upper surface to the lower surface with respect to a virtual straight line connecting the respective centers of the upper and lower surfaces. An inclination angle of the inclined surface with respect to a virtual straight line on the side surface increases from a portion of the inclined surface which is continuous with an end portion of the major cutting edge to a portion of the inclined surface which is continuous with a center of the major cutting edge.

A method of manufacturing a machining tool in which an insert holder comprises a first surface, a second surface opposite the first surface, and a first insert tip slot extending between the first surface and the second surface. The first insert tip slot is configured so as to be compressed and densified to support a first insert tip. The insert holder further includes elevated projections extending from the first and second surfaces proximate the first insert tip slot.

A lathe has a plurality of turret positions with at least one having a toolholder, a pair of blades projecting from one end of the toolholder with the toolholder structured to assume a first position with a first blade machining said workpiece which is rotating in a first direction and a second position with a second blade structured to assume a second position with the workpiece rotating in the other direction. The toolholder remains fixed during machining. Related methods and toolholders are disclosed.

A cutting insert includes an upper surface, a lower surface, a side surface, and an upper cutting edge. The upper cutting edge includes a major cutting edge having an outwardly projecting curvilinear shape, and a minor cutting edge having a straight line shape and being continuous with the major cutting edge. The side surface includes a continuous inclined surface with the major cutting edge and is inclined outward from the upper surface to the lower surface with respect to a virtual straight line connecting the respective centers of the upper and lower surfaces. An inclination angle of the inclined surface with respect to a virtual straight line on the side surface increases from a portion of the inclined surface which is continuous with an end portion of the major cutting edge to a portion of the inclined surface which is continuous with a center of the major cutting edge.

A cutting insert includes an upper surface, a lower surface, a side surface, and an upper cutting edge. The upper cutting edge includes a major cutting edge having an outwardly projecting curvilinear shape, and a minor cutting edge having a straight line shape and being continuous with the major cutting edge. The side surface includes a continuous inclined surface with the major cutting edge and is inclined outward from the upper surface to the lower surface with respect to a virtual straight line connecting the respective centers of the upper and lower surfaces. An inclination angle of the inclined surface with respect to a virtual straight line on the side surface increases from a portion of the inclined surface which is continuous with an end portion of the major cutting edge to a portion of the inclined surface which is continuous with a center of the major cutting edge.