Cutting insert

A cutting insert comprising

• a rake face;
• a flank face continuous with the rake face;
• and
• a seating surface opposite to the rake face, wherein
• a ridge line between the rake face and the flank face forms a cutting edge,
• the cutting edge includes
• a nose portion,
• a first cutting edge portion continuous with one end of the nose portion and having a linear shape, and
• a second cutting edge portion continuous with another end of the nose portion and having a linear shape,
• the rake face is provided with a first projection, a second projection, a third projection, and a fourth projection,
• the first projection and the second projection are located on a bisector with an angle formed between the first cutting edge portion and the second cutting edge portion as viewed from a direction perpendicular to the seating surface, and the first projection is located between the nose portion and the second projection,
• the third projection and the fourth projection are located on a first straight line inclined with respect to the bisector as viewed from the direction perpendicular to the seating surface, and
• the third projection is located between the second cutting edge portion and the fourth projection,
• in a first cross section including the bisector and perpendicular to the seating surface, the rake face has
• a first inclined portion located between the first projection and the nose portion,
• a first breaker portion continuous with the first inclined portion and forming a surface of the first projection,
• a first step surface rising from the first breaker portion, and a second breaker portion continuous with the first step surface and forming a surface of the second projection,
• in a second cross section including the first straight line and perpendicular to the seating surface, the rake face has
• a second inclined portion located between the third projection and the second cutting edge portion,
• a third breaker portion continuous with the second inclined portion and forming a surface of the third projection,
• a second step surface rising from the third breaker portion, and
• a fourth breaker portion continuous with the second step surface and forming a surface of the fourth projection, and
• when a boundary between the first inclined portion and the first breaker portion, a boundary between the first step surface and the second breaker portion, a boundary between the second inclined portion and the third breaker portion, and a boundary between the second step surface and the fourth breaker portion are a first position, a second position, a third position, and a fourth position, respectively,
• in the direction perpendicular to the seating surface, the second position is higher than the first position, and the fourth position is higher than the third position, and
• in a direction parallel to the seating surface and perpendicular to the first straight line, a distance between the first position and the third position is greater than a distance between the second position and the fourth position.