Abstract: A diamond segment or insert for the cutting of hard materials and provided with dead holes formed in one of its faces and shaped and distributed in such a way that all the cross-sections perpendicular to the longitudinal axis of the tool originate full surfaces whose areas are all substantially equal to each other and in a constant ratio with the area of the rated cross-section of the tool, whatever the degree of wear of the tool may be; the holes have a depth greater than half the thickness of the tool and are disposed on the disk or the tool intended to be used for the cutting alternately turned through 180.degree. with respect to each other; the holes may be filled with an aphonous abrasive or superabrasive material.