Provided is a cutting insert which is resistant to breakage and can stably be restrained. A cutting insert configured as a vertically mounted insert has a first rake face adjacent to a first major cutting edge, a second rake face adjacent to a second major cutting edge, a restraint surface located further inward than the first and second rake faces to come into contact with a tool body when a second end surface is used, and a reinforcing portion projecting from the restraint surface. The reinforcing portion has a third projecting ridge provided to extend between the first and second rake faces and halve the restraint surface, a first projecting ridge connected to one end of the third projecting ridge to extend so as to cover at least a portion of a boundary between the first rake face and the restraint surface, and a second projecting ridge connected to another end of the third projecting ridge so as to cover at least a portion of a boundary between the second rake face and the restraint surface.

A rotary cutting tool for slotting and a cutting insert replaceably mounted to such a rotary cutting tool. The cutting insert is mounted to an insert pocket of a tool body of the rotary cutting tool and is pressed by an elastic pressure portion provided in the tool body. The cutting insert has an upper surface, a lower surface and four peripheral side surfaces. The top and lower surfaces have an inclined surface pressed by the elastic pressure portion. When the cutting insert is mounted to the insert pocket, the inclined surface of the upper surface is pressed by the elastic pressure portion. The inclined surface is inclined with respect to a cross section of the cutting insert such that the lower surface and two peripheral side surfaces of the cutting insert are contacted with the insert pocket by pressure of the elastic pressure portion.

An insert may include a first surface, a second surface, a ridge line located at an intersection of the first surface and the second surface. The first surface may include a first corner, a first side and a second side. The ridge line may include a corner cutting edge located on the first corner, a first cutting edge located on the first side, and a second cutting edge located on the second side. The first surface may further include a first region located from the first cutting edge toward a midportion of the first surface, a second region located from the second cutting edge toward the midportion of the first surface, and a concave part located on at least one of the first region and the second region.

A cutting insert includes a body having an upper face, a lower face, a plurality of planar flank faces, bidirectional acute cutting corners and bidirectional obtuse cutting corners joining two adjacent flank faces. A land has a varying width. An annular island includes a plurality of bulged extensions, relatively longer and narrower chip breaking points proximate the acute cutting corners, and relatively shorter and wider chip breaking points proximate the obtuse cutting corners. A chip breaking ramp surface flanks each of the relatively longer and narrower chip breaking points and each of the relatively shorter and wider chip breaking points. The chip breaking ramp surfaces form a series of non-collinear lines that are at a non-zero angle with respect to the cutting edge.

A blade positioning structure of a disposable milling cutter includes a cutter body and a disposable blade. The cutter body is peripherally provided with a blade seat. By passing a screw through the disposable blade and the blade seat, the disposable blade is locked to the blade seat. The blade seat has a blade seat surface and a sidewall; the blade seat surface has a groove; the disposable blade has a bottom surface provided with a projection corresponding in shape to the groove; and when the disposable blade is locked to the blade seat, the blade seat surface and the groove of the latter lie respectively and tightly against the bottom surface and the projection of the former.

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.

An insert may include a first surface, a second surface, a ridge line located at an intersection of the first surface and the second surface. The first surface may include a first corner, a first side and a second side. The ridge line may include a corner cutting edge located on the first corner, a first cutting edge located on the first side, and a second cutting edge located on the second side. The first surface may further include a first region located from the first cutting edge toward a midportion of the first surface, a second region located from the second cutting edge toward the midportion of the first surface, and a concave part located on at least one of the first region and the second region.

A cutting insert includes a main surface formed in a substantially parallelogram shape and having a pair of acute angle corner portions and a pair of obtuse angle corner portions, a seating surface that faces a side opposite to the main surface, a side surface that connects the main surface and the seating surface to each other, a corner cutting edge disposed in the acute angle corner portion, and a main cutting edge and a subsidiary cutting edge which are respectively disposed in a pair of side ridge portions of the main surface located each other across the acute angle corner portion. A mounting hole into which the fixing member is inserted penetrates the main surface and the seating surface. The main cutting edge is inclined at an inclination angle equal to or larger than 8° with reference to a plane perpendicular to an axial direction of the mounting hole.

An insert may include a first surface, a second surface, a ridge line located at an intersection of the first surface and the second surface. The first surface may include a first corner, a first side and a second side. The ridge line may include a corner cutting edge located on the first corner, a first cutting edge located on the first side, and a second cutting edge located on the second side. The first surface may further include a first region located from the first cutting edge toward a midportion of the first surface, a second region located from the second cutting edge toward the midportion of the first surface, and a concave part located on at least one of the first region and the second region.

Provided is a cutting insert which is resistant to breakage and can stably be restrained. A cutting insert configured as a vertically mounted insert has a first rake face adjacent to a first major cutting edge, a second rake face adjacent to a second major cutting edge, a restraint surface located further inward than the first and second rake faces to come into contact with a tool body when a second end surface is used, and a reinforcing portion projecting from the restraint surface. The reinforcing portion has a third projecting ridge provided to extend between the first and second rake faces and halve the restraint surface, a first projecting ridge connected to one end of the third projecting ridge to extend so as to cover at least a portion of a boundary between the first rake face and the restraint surface, and a second projecting ridge connected to another end of the third projecting ridge so as to cover at least a portion of a boundary between the second rake face and the restraint surface.