Patent ID: 8192113

Claim:
A drill for chip removing machining, comprising: a drill body that rotates around a center axis (C 1 ) and has a rear end, and a front end from which there extends rearward an envelope surface in which two chip flutes each having an insert pocket are countersunk; and two replaceable cutting inserts, including a peripheral cutting insert mounted in a peripheral pocket, and a center insert, which is indexable and mounted in a center pocket that opens in the front end of the drill body and is delimited by a bottom surface, a rear end support surface, a side support surface of a partition wall, and an inside of a border adjacent to the envelope surface; the center insert including an upperside and an underside between which a through hole for a tightening screw extends, and having an elongate basic shape that is mirror-symmetrical in relation to an imaginary, longitudinal central plane (P) with which a center axis (C 3 ) of the hole coincides such that the central plane (P) divides the shape into two portions, a first portion being symmetrical with a second portion in relation to the central plane (P) when the first portion is inverted about an axis orthogonal to the central plane (P), and one of two opposite, longitudinal side contact surfaces of the cutting insert which run parallel to each other and to the central plane (P), being urged against the side support surface of the center pocket, and one of the two opposite end surfaces which are formed adjacent to chip-removing cutting edges at the short ends of the center insert, being urged against the rear end support surface of the center pocket; wherein the side support surface of the center pocket is inclined in relation to the center axis (C 1 ) of the drill body at an acute angle (ε) within the range of 3-8°; and wherein, at each one of two diagonally opposite corners of the center insert, an intermediate surface is formed between the side contact surface and an end surface, the intermediate surface being shorter than the side contact surface and forming an obtuse angle (α) with the side contact surface, one of the intermediate surfaces being located in an area of a clearance space between the side support surface of the center pocket and the end support surface of the center pocket.