Patent ID: 6935814

Claim:
A throwaway cutting tool comprising: a cutting tool main body which is rotatable about an axis of rotation, and which has a distal end and a proximal end; and a throwaway insert comprising: an insert body formed in a polygonal shape; and a cutting face formed by a polygonal face of the insert body; a corner cutting edge which is formed in a curved shape at a corner of the cutting face; and a major cutting edge which is formed along a side edge of the cutting face that is connected to a first end of the corner cutting edge; and a concave portion which is formed, in another side edge of the cutting face adjacent to the second end of the corner cutting edge, and so as to be made concave toward the inside of the cutting face from a tangent of the corner cutting edge drawn at the second end of the corner cutting edge, wherein the throwaway insert is detachably attached to an outer periphery of the distal end of the cutting tool main body in such a manner that the cutting face thereof is directed in the direction of rotation of the cutting tool main body; wherein the corner cutting edge thereof is disposed at the distal end of the cutting tool main body while being projected radially and outwardly from the distal end; wherein the major cutting edge connected to the first end of the corner cutting edge is projected distally from the cutting tool main body while being inclined so as to depart from the distal end as the distance from the first end of the corner cutting edge increases, and the distance from the center of the cutting tool main body decreases; and wherein the tangent drawn at the second end of the corner cutting edge is inclined toward the inside of the cutting tool main body as the distance from the proximal end of the cutting tool main body.