A cutting tool assembly includes: a cutter body extending perpendicularly from a bottom surface and including a cylindrical portion with a rotational axis; insert pockets disposed and formed concavely in the bottom surface and the cylindrical portion to be spaced apart from each other along a circumferential direction; fixed cutting inserts mounted within the insert pockets and disposed at the outermost portion of the cutter body in a radial direction; and stepped cutting inserts mounted within the insert pockets, the stepped cutting insert being disposed between two adjacent fixed cutting inserts. The fixed cutting insert is disposed to have an identical length from the rotational axis and an identical length from the bottom surface. At least one stepped cutting insert is disposed to have a different length from the rotational axis and a different length from the bottom surface compared to the remaining stepped cutting inserts.

A cutting insert has opposing first and second end surfaces, and a peripheral side surface (connecting the end surfaces. A central axis penetrates the two end surfaces. The peripheral sure surface includes an outwardly inclined first side surface part related to a major cutting edge and a second side surface part related to a minor cutting edge. The outwardly inclined first side surface part gradually extends outward from the cutting insert, heading from the first end surface to the second end surface. When a second virtual plane, which is substantially perpendicular to the central axis and passes through the major cutting edge, is defined, an inwardly inclined part, on a back side of the cutting edge, of the second end surface is inclined so as to become more distant from the second virtual plane, heading from the outwardly inclined first side surface part to the central axis.

A cutting insert includes a cutting edge having an involute-curve approximate shape. A cutting edge is formed so as to wholly take on a first curved shape with a first curvature radius when the cutting insert is viewed from the end surface, and is formed so that a large part of the cutting edge takes on a second curved shape with a second curvature radius when the cutting insert is viewed from the side surface.

A cutting insert includes an end cutting edge, a first major cutting edge, and a second major cutting edge. The height of the end cutting edge relative to an imaginary plane orthogonal to a central axis of a through-hole is fixed. The height of the first major cutting edge relative to the imaginary plane increases, when viewed from a side, moving away from the end cutting edge. The height of the second major cutting edge relative to the imaginary plane decreases, when viewed from a side, moving away from the first major cutting edge. When viewed from a side, the angle of inclination, relative to the imaginary plane, of an imaginary line connecting both ends of the second major cutting edge is greater than an angle of inclination, relative to the imaginary plane, of an imaginary line connecting both ends of the first major cutting edge.

A cutting insert of an embodiment includes an upper surface including a first upper cutting edge and a second upper cutting edge, a lower surface including a first lower cutting edge and a second lower cutting edge, and a side surface. The side surface includes a first surface extending from the second upper cutting edge, a second surface extending from the first lower cutting edge, a third surface extending from the first upper cutting edge, and a fourth surface extending from the second lower cutting edge. The first surface and the fourth surface are parallel to a central axis. The second surface is inclined so as to depart from the central axis as going from the lower surface toward the upper surface. The third surface is inclined so as to depart from the central axis as going from the upper surface toward the lower surface.

An insert includes a rake angle set corresponding to the hardness of a material to be cut and that can suppress an increase in the material cost even when the strength of a cut edge section is increased. The insert has a polygonal shape and includes a cutting edge portion on at least one side of the polygonal shape. The cutting edge portion includes a rake face having a convex formed on one of opposite surfaces in the thickness direction a flank face having a concave formed on a surface intersecting with the one surface in the thickness direction and a concave cutting edge that is formed between the rake face and the flank face.

A milling insert suitable for shoulder milling includes a side surface extending between an upper and lower side and a cutting edge having a primary and a secondary cutting edge portion. The side surface includes an axial support surface opposite of the secondary cutting edge portion. The lower side includes a locking groove extending longitudinally, and a lower contact region formed to bear on a fastening member. The upper side has an upper contact region arranged to bear on a top support member of a tool in which the milling insert is mountable. A milling tool is provided with a top support member for bearing on the upper contact region of the milling insert, a locking ridge for locking with the locking groove, and an axial contact surface for supporting the axial support surface. A fastening member presses the milling insert against the top support member and the locking ridge.

A reversible cutting insert for milling has first and second cutting edges formed at the transitions from the top and bottom surfaces to a lateral face. The cutting insert has a 4-fold rotational symmetry. A reference plane extends perpendicular to the axis of symmetry. The cutting edges have four cutting edge portions. One cutting edge portion is a main edge and a wiper edge that are connected by a rounded cutting corner. The first and second cutting edges are at the greatest distance from the reference plane in the region of the cutting corners. Main and wiper clearance faces directly adjoin an assigned main edge and wiper edge, respectively, in the circumferential lateral face. Exterior angles between the main clearance faces and the reference plane are greater than exterior angles between the wiper clearance faces and the reference plane.

A cutting insert includes: two opposite end surfaces; a peripheral side surface extending between the end surfaces; and plural cutting edge sections that are formed along an intersecting ridgeline portion between the peripheral side surface and each of the end surfaces. Each of the cutting edge sections includes a corner cutting edge, a major cutting edge, and a minor cutting edge. A non-cutting intersecting ridgeline area extending between adjacent cutting edge sections on one end surface is located adjacent, via the peripheral side surface, to at least a part of the corner cutting edge and the major cutting edge of an associating cutting edge section on the other end surface.

A double-sided, trigon cutting insert has three three major cutting edges formed at an intersection between a first planar side surface portion and first and second surfaces, and three minor cutting edges formed at an intersection between a second planar side surface portion and first and second surfaces. A planar rake surface extends radially inward and downward from each major cutting edge, and a rounded rake surface extends radially inward and downward from each minor cutting edge. An insert-receiving pocket of a cutting tool includes a planar bottom support surface, a first planar side support surface, a second planar side support surface, and a third planar side support surface. Each rounded rake surface is formed with a radius, R, that causes only a high point of each minor cutting edge to contact a workpiece during a machining operation.