US Patent 10300536 Cutting tool and indexable rotary cutting tool

A cutting insert including a first end surface, a second end surface and a peripheral side surface extending therebetween. The first and second end surfaces each having one substantially quadrangular portion and two substantially semicircular portions which are respectively joined to two opposing sides of the substantially quadrangular portion. An intersecting edge between each of the first and second end surfaces and the peripheral side surface is provided with a cutting edge. The cutting edge is formed in at least part of the substantially semicircular portion. At least part of a portion of the peripheral side surface which is adjacent to the substantially quadrangular portion of each of the first and second end surfaces, and at least part of a portion of the peripheral side surface which is adjacent to the substantially semicircular portion, each have a function of coming into contact with an insert seat.