End mill

An end mill comprising first cutting edges which spiral in a direction defining a positive helix angle and second cutting edges which spiral in a direction defining a negative helix angle, the first cutting edges and the second cutting edges being disposed at positions shifted in a circumferential direction,

• wherein the first cutting edges and the second cutting edges are each configured to be continuous over an effective cutting edge length,
• wherein, at an axially forward end of the end mill, a first phase angle between one of the first cutting edges and its adjacent second cutting edge located adjacent to the first cutting edges in an opposite direction to a tool rotation direction is set to be different from a second phase angle between the second cutting edge and its adjacent first cutting edge located adjacent to the second cutting edges in the opposite direction to the tool rotation direction,
• wherein the first cutting edges and the second cutting edges are disposed alternately in the circumferential direction,
• wherein the first phase angle between one of the first cutting edges and its adjacent second cutting edge located adjacent to the one first cutting edge in the opposite direction to the tool rotation direction is set larger than the second phase angle between the second cutting edge and its adjacent first cutting edge located adjacent to the second cutting edge in the opposite direction to the tool rotation direction,
• wherein the helix angle of the first cutting edges is set larger than the helix angle of the second cutting edges, and
• wherein the helix angle of the first cutting edges is set at 3° to 10°, and the helix angle of the second cutting edges is set at −3° to −10°.