Abstract: A reaming tool having a single blade in the head portion of its shank is provided with two axially elongated guide ribs radially and axially approximately coextensive with the cutting edge of the blade. One guide rib is diametrically opposite the cutting edge, and the other one is much nearer to the cutting edge than to the other rib so that the angular center-to-center spacing of the two ribs is bisected by the resultant force defined by the circumferential cutting force exerted by the cutting edge on a body of mild steel during reaming at a cutting speed of 5 to 100 meters per minute and at an axial feed rate of 0.1 to 0.5 mm per revolution, and the radially inward force of reaction acting on the cutting blade during the reaming.

Abstract: An expanding machine reamer whose cutter head has an imperforate core portion and three axially elongated rib portions radially projecting from the core portion in circumferentially spaced relationship. The rib portions are each formed with three bores approximately perpendicular to a common axial plane. A first bore receives a clamping screw engaging a clamping shoe which holds a cutting blade against a flank of the rib portion, second and third bores hold wedge-shaped abutment members radially engaging the blade and backing screws by means of which the radial position and the inclination of the cutting edge of the blade may be adjusted.