A cutting insert according to one aspect has a flat plate shape including a first main surface having a polygonal shape, a second main surface located opposite to the first main surface, and an outer peripheral surface located between the first main surface and the second main surface. The cutting insert includes a cutting portion located in regions including at least a corner portion of the first main surface, and a main body portion located in a region other than the corner portion. A thickness of the main body portion is larger than a thickness of the cutting portions, and the main body portion includes a recessed portion or a protruding portion located in the outer peripheral surface thereof.

In a cutting tool having an indexable lay-down cutting insert with a central body portion and three circumferentially spaced apart cutting portions, the cutting insert is removably secured to an elongated holding portion of an insert holder. Each cutting portion has a cutting edge with first and second cutting end points, the cutting edge formed at the intersection of an upward facing rake surface and a radially outward facing relief surface. In a top view of the cutting insert, parallel imaginary first and second vertical planes containing the first and second cutting end points, intersect the central body portion at first and second body side points, which are located first and second cutting distances from the first and second cutting end points, respectively. Each of the first and second cutting distances is greater than twenty-five percent of the first radius of an imaginary first circle circumscribing the cutting insert.

To provide a cutting insert such that a tool body can sufficiently hold the cutting insert even if one of cutting parts is broken. The cutting insert includes two side surfaces opposed to each other, a fixing hole passing through the centers of the two side surfaces, and an outer circumferential surface that is disposed between the outer circumferential edges of the two side surfaces and are connected to the outer circumferential edges of the two side surfaces. The outer circumferential surface includes four cutting parts, a first outer circumferential surface part that is disposed between the first cutting part and the second cutting part, and a second outer circumferential surface part that is opposed to the first outer circumferential surface part and is disposed between the third cutting part and the fourth cutting part. In a side view of the side surfaces from the axial direction of the fixing hole, the first outer circumferential surface part and the second outer circumferential surface part each have the center recessed toward the fixing hole, and a virtual arc having the same diameter as the diameter of the circumcircle of the cutting insert is in contact with two points on each of the outer circumferential surface parts.

A tool body to which a replaceable cutting insert is fixed includes: a holder: an insert mounting seat that is provided on a first surface of the holder; a clamp member that constrains the cutting insert placed on the insert mounting seat; and an operating member that presses a pressure receiving surface of the clamp member. The clamp member has the pressure receiving surface, a spherical head portion that is formed into a spherical crown shape, and a hook portion that protrudes to a side opposite to a side of the spherical head portion when seen from a side of the first surface. The insert mounting seat supports the clamp member to be swingable with the spherical head portion as a fulcrum, and the hook portion contacts a diameter reducing portion that is formed on an inner peripheral surface of an mounting hole for the cutting insert in a state in which the pressure receiving surface is pressed.

A cutting insert and a cutting tool which can suppress lowering of blade-edge positional accuracy while holding by a holder having a small thickness is enabled are provided.

The cutting insert includes a first end surface, a second end surface, and a peripheral side surface connected to the first end surface and the second end surface and having a rake face, a flank, and a cutting edge formed in a connection region between the rake face and the flank, and a through hole penetrating the first end surface and the second end surface is formed. It is the cutting insert including a first contact surface substantially perpendicular to a center axis direction of the through hole and capable of contacting the holder, a second contact surface substantially in parallel with the center axis direction of the through hole, substantially perpendicular to a plane including the first contact surface and capable of contacting the holder, and a third contact surface inclined with respect to the center axis direction of the through hole and capable of contacting the holder, and a cutting tool including the cutting insert as above.

A tool system for machining includes a tool body that has a first end for connecting to a machine tool and a second end having an end face on which a seat for an interchangeable cutting insert is formed. The cutting insert has an underside formed as an abutment surface, a top side formed as a rake face, and an encircling side face formed as a flank, and a cutting edge is formed at a transition from the top side to the encircling side face. The cutting insert is arranged on the seat such that the top side extends perpendicularly to the longitudinal axis of the tool body and the cutting edge protrudes beyond the outer circumference of the end face of the tool body in a radial direction with respect to the longitudinal axis with two usable cutting corners and cutting-corner portions adjoining the latter on both sides.

An indexable cutting insert for a cutting tool for material processing machines has a first axis of symmetry, at least one fastening bore passing through the indexable cutting insert parallel or coaxially to this first axis, two groups of main cutting edges, secondary cutting edges and cutting corners having a second axis of symmetry rotationally symmetrically opposite one another. At least the main cutting edges enclose an acute cutting edge angle with a plane oriented orthogonally to the first axis of symmetry. A cutting insert holder holds and fixes an indexable cutting insert. A recess for receiving the indexable cutting insert is on an elongated base body with polygonal cross-section. A support surface for supporting the indexable cutting insert is rotated about the base-body longitudinal axis and tilted about a second axis, a line of intersection between the rotated support surface and a plane perpendicular to the longitudinal axis.

A cutting insert and a cutting tool which can suppress lowering of blade-edge positional accuracy while holding by a holder having a small thickness is enabled are provided. The cutting insert includes a first end surface, a second end surface, and a peripheral side surface connected to the first end surface and the second end surface and having a rake face, a flank, and a cutting edge formed in a connection region between the rake face and the flank, and a through hole penetrating the first end surface and the second end surface is formed. It is the cutting insert including a first contact surface substantially perpendicular to a center axis direction of the through hole and capable of contacting the holder, a second contact surface substantially in parallel with the center axis direction of the through hole, substantially perpendicular to a plane including the first contact surface and capable of contacting the holder, and a third contact surface inclined with respect to the center axis direction of the through hole and capable of contacting the holder, and a cutting tool including the cutting insert as above.

A tool system for machining includes a tool body that has a first end for connecting to a machine tool and a second end having an end face on which a seat for an interchangeable cutting insert is formed. The cutting insert has an underside formed as an abutment surface, a top side formed as a rake face, and an encircling side face formed as a flank, and a cutting edge is formed at a transition from the top side to the encircling side face. The cutting insert is arranged on the seat such that the top side extends perpendicularly to the longitudinal axis of the tool body and the cutting edge protrudes beyond the outer circumference of the end face of the tool body in a radial direction with respect to the longitudinal axis with two usable cutting corners and cutting-corner portions adjoining the latter on both sides.

In a cutting tool having an indexable lay-down cutting insert with a central body portion and three circumferentially spaced apart cutting portions, the cutting insert is removably secured to an elongated holding portion of an insert holder. Each cutting portion has a cutting edge with first and second cutting end points, the cutting edge formed at the intersection of an upward facing rake surface and a radially outward facing relief surface. In a top view of the cutting insert, parallel imaginary first and second vertical planes containing the first and second cutting end points, intersect the central body portion at first and second body side points, which are located first and second cutting distances from the first and second cutting end points, respectively. Each of the first and second cutting distances is greater than twenty-five percent of the first radius of an imaginary first circle circumscribing the cutting insert.