A end mill includes: an end mill body having a rotation axis, the end mill body including a shank portion and a cutting portion with an outer peripheral cutting edge; an end cutting edge including a first cutting edge and a second cutting edge; a first gash opening between the first cutting edge and the second cutting edge; and a second gash located adjacently to the first gash in the rotational direction, and opening to a side closer to the outside peripheral from the chisel portion. A ratio (L1/L2) of a length (L1) from a distal end of the end mill body to a terminal end of the first gash to a length (L2) from the distal end of the end mill body to a terminal end of the second gash, when viewed from a side, is from 0.8 to 1.1.

There is provided a cutting insert which is capable of cutting by using either one of both surfaces and is stably supported by a tool body. Each of a first end surface and a second end surface of a cutting insert includes a first inclined surface which is inclined from a diagonal line by which a corner portion connecting a first peripheral side surface and a second peripheral side surface and a corner portion connecting a third peripheral side surface and a fourth peripheral side surface are joined toward a corner portion connecting the first peripheral side surface and the fourth peripheral side surface such that a distance to an imaginary plane decreases, and a second inclined surface which is inclined from the diagonal line toward a corner portion connecting the second peripheral side surface and the third peripheral side surface such that a distance to the imaginary plane decreases.

There is provided a cutting insert which is capable of cutting by using either one of both surfaces and is stably supported by a tool body. Each of a first end surface and a second end surface of a cutting insert includes a first inclined surface which is inclined from a diagonal line by which a corner portion connecting a first peripheral side surface and a second peripheral side surface and a corner portion connecting a third peripheral side surface and a fourth peripheral side surface are joined toward a corner portion connecting the first peripheral side surface and the fourth peripheral side surface such that a distance to an imaginary plane decreases, and a second inclined surface which is inclined from the diagonal line toward a corner portion connecting the second peripheral side surface and the third peripheral side surface such that a distance to the imaginary plane decreases.

A end mill includes: an end mill body having a rotation axis, the end mill body including a shank portion and a cutting portion with an outer peripheral cutting edge; an end cutting edge including a first cutting edge and a second cutting edge; a first gash opening between the first cutting edge and the second cutting edge; and a second gash located adjacently to the first gash in the rotational direction, and opening to a side closer to the outside peripheral from the chisel portion. A ratio (L1/L2) of a length (L1) from a distal end of the end mill body to a terminal end of the first gash to a length (L2) from the distal end of the end mill body to a terminal end of the second gash, when viewed from a side, is from 0.8 to 1.1.

In an end mill, a peripheral cutting edge portion has a peripheral cutting edge formed in a spiral shape around an axis, a peripheral rake face formed on the front side of the peripheral cutting edge in the rotating direction and bordering thereon and a peripheral flank formed on the rear side of the peripheral cutting edge in the rotating direction and bordering thereon. The peripheral flank has a first peripheral flank formed in a position on the mill body tip side to have a first clearance angle and a second peripheral flank formed in a position on the mill body end side of the first peripheral flank and neighboring the first peripheral flank to have a second clearance angle. An average width value of the first peripheral flank in the rotating direction is greater than an average width value of the second peripheral flank in the rotating direction.

A milling cutter includes a cutting section extending from a shank along an axis. The shank includes a free end as a first end of the milling cutter. The cutting section includes a free end as a second end of the milling cutter. The cutting section includes at least one right-hand cutting unit, at least one left-hand cutting unit and at least two grooves about the axis. Each of the grooves is made between the right-hand cutting unit and the left-hand cutting unit. The right-hand cutting unit includes several right-hand blades extending at a first helical angle relative to the axis. The left-hand cutting unit includes several left-hand blades extending at a second helical angle relative to the axis.

A two-flute ball end mill includes a cutting edge that is formed at an intersection ridge line between a groove wall surface of a gash groove and a flank surface; and the flank surface includes a first flank surface that forms a chisel edge and a second flank surface that extends from the first flank surface to a rear side in a rotation direction with a larger clearance angle. In a case where, as seen from a tip side in an axial direction, an intersection point between one cutting edge of two cutting edges and the chisel edge is defined as a first intersection point, and an intersection point between a flank surface boundary line between the first flank surface and the second flank surface of the other cutting edge of the cutting edges and the groove wall surface is defined as a second intersection point.