The cutting device includes a rotating portion for rotating the cutting tool in a rotation axis line of the cutting tool and a traveling means for making the cutting tool travel relative to a workpiece. The rotating means and the traveling means rotates the outer peripheral surface of the cutting tool and makes the cutting tool travel, having the outer peripheral surface function as the rake surface, so as to perform cutting machining.

A cutting insert has a cutting edge formed at an intersection of a rake surface and a relief surface, with a chip-control arrangement located at the rake surface. The chip-control arrangement includes a depression that includes a depression declining surface that extends downwardly in a direction away from the major cutting edge. A chip deflecting surface located rearward of the depression is inclined upwardly in a direction away from the major cutting edge. A chip former includes an interposed projection that extends from the chip deflecting surface to the depression declining surface, and two lateral protuberances that extend from opposite sides of the interposed projection to the depression declining surface beyond a forwardmost portion of the interposed projection.

A machining tool is rotated around an axis and includes a machining blade portion having a first machining blade in the distal end direction with respect to a rake face and a second machining blade located in the radially outward direction with respect to the rake face, and a protrusion formed on the rake face and having a tip for cutting chips coming from the first machining blade. The protrusion includes an inner forming portion that is located in the radially inward direction from the reference line and an outer forming portion that is located in the radially outward direction from the reference line, and the width of the inner forming portion is wider than the width of the outer forming portion.

A machining tool is rotated around an axis and includes a machining blade portion having a first machining blade in the distal end direction with respect to a rake face and a second machining blade located in the radially outward direction with respect to the rake face, and a protrusion formed on the rake face and having a tip for cutting chips coming from the first machining blade. The protrusion includes an inner forming portion that is located in the radially inward direction from the reference line and an outer forming portion that is located in the radially outward direction from the reference line, and the width of the inner forming portion is wider than the width of the outer forming portion.

A cutting insert may include an upper surface, a lower surface, a front cutting edge and a first lateral cutting edge. The upper surface may include a breaker protrusion. The first lateral cutting edge may include an inclined part which is closer to the lower surface as going away from the front cutting edge. The breaker protrusion may include a first region, a second region and a third region. The first region may be located further away from the lower surface than the inclined part. The second region may be located closer to the front cutting edge than the first region, and may be located closer to the lower surface than the inclined part. The third region may be located further away from the front cutting edge than the first region, and may be located closer to the lower surface than the inclined part.

A cutting insert may include an upper surface, a lower surface, a front cutting edge and a first lateral cutting edge. The upper surface may include a breaker protrusion. The first lateral cutting edge may include an inclined part which is closer to the lower surface as going away from the front cutting edge. The breaker protrusion may include a first region, a second region and a third region. The first region may be located further away from the lower surface than the inclined part. The second region may be located closer to the front cutting edge than the first region, and may be located closer to the lower surface than the inclined part. The third region may be located further away from the front cutting edge than the first region, and may be located closer to the lower surface than the inclined part.

A cutting insert may include an upper surface, a side surface, and a cutting edge. The upper surface may include a first breaker portion and a second breaker portion. The first breaker portion may include a first surface inclined downward and a second surface inclined upward. The second breaker portion may be inclined upward as the second breaker portion extends away from the first breaker portion. An inclination angle of the first surface may be constant along the first side portion. A length of the first surface may be greater at a second end portion than at a first end portion. An intersection portion of the first breaker portion and the second breaker portion may be orthogonal to the first side portion, or inclined away from the first corner portion as the intersection portion extends away from the first side portion.

A cutting insert may include an upper surface, a side surface, and a cutting edge. The upper surface may include a first breaker portion and a second breaker portion. The first breaker portion may include a first surface inclined downward and a second surface inclined upward. The second breaker portion may be inclined upward as the second breaker portion extends away from the first breaker portion. An inclination angle of the first surface may be constant along the first side portion. A length of the first surface may be greater at a second end portion than at a first end portion. An intersection portion of the first breaker portion and the second breaker portion may be orthogonal to the first side portion, or inclined away from the first corner portion as the intersection portion extends away from the first side portion.

The upper surface includes a first breaker projection face extending along the first side surface, a second breaker projection face extending along the second side surface, and a rake face located between the first breaker projection face and the second breaker projection face in top view. In a direction from the rear surface to the front surface, a first front end of the first breaker projection face is located ahead of a second front end of the second breaker projection face. A cutting edge has a first cutting edge portion and a second cutting edge portion. In a direction perpendicular to the reference surface, the second breaker projection face is lower than the first breaker projection face, and a boundary between the first cutting edge portion and the second cutting edge portion is lower than the second breaker projection face.

The upper surface includes a first breaker projection face extending along the first side surface, a second breaker projection face extending along the second side surface, and a rake face located between the first breaker projection face and the second breaker projection face in top view. In a direction from the rear surface to the front surface, a first front end of the first breaker projection face is located ahead of a second front end of the second breaker projection face. A cutting edge has a first cutting edge portion and a second cutting edge portion. In a direction perpendicular to the reference surface, the second breaker projection face is lower than the first breaker projection face, and a boundary between the first cutting edge portion and the second cutting edge portion is lower than the second breaker projection face.