US Patent 8192113 Indexable insert drill and a center insert therefore

A drill includes a center insert which is indexable, mounted in a center pocket, and has an elongate basic shape. One of two opposite longitudinal side contact surfaces of the cutting insert which run parallel to each other are urged against the side support surface of the center pocket. The side support surface of the center pocket is inclined in relation to the center axis of the drill body at an acute angle within the range of 3-8 degrees. An intermediate surface is formed between the side contact surface and an end surface. The intermediate surface is shorter than the side contact surface and forms an obtuse angle with the side contact surface.