Abstract: A ball end mill including an elongated body, a center insert, and a plurality of cutting inserts. The center insert and the cutting inserts are mounted on the forward end of the body. The center insert and each of the cutting inserts are adjacent to each other in such a manner that the center insert is located with a part thereof at the center. The center insert which is made of cemented carbide has cutting edges passing through the center axis. The cutting inserts are made of a super hard sintered compact. Each of the cutting inserts has a cutting edge aligned to the cutting edge of the center insert. The cutting edges of the cutting inserts and the center insert cooperate to draw a hemispherical path on rotation.

Abstract: An insert boring tool includes radially outward and inward cutting inserts mounted thereon. The radially outward and inward inserts are arranged such that end cutting edges of the respective inserts are intersected with each other at a point of intersection in loci of rotation of the respective inserts in a plane containing an axis of a tool body. The radially outward and inward inserts are positioned such that, assuming that a radial distance between the point of intersection and a radially outermost end of the end cutting edge of the radially outward insert is A, and a radial distance between the point of intersection and a radially innermost end of the end cutting edge of the radially inward insert is B, a ratio of A/B takes a value of from 2/8 to 45/55.