Abstract: A tool for opening fiber bales in which a plurality of axially spaced blades are mounted coaxially on a shaft. Each of the blades has a periphery provided with projecting sawteeth which engage the fibers of a bale to be opened. Each of the sawteeth is bounded by two flanks which include a predetermined angle between themselves. There is also a predetermined circumferential spacing between the tips of successive fronts of the sawteeth. A leading flank and a trailing flank are arranged so that the leading flank is inclined in the direction of rotation. The angle of inclination of the leading flank with reference to a straight-line intersecting the tip of the respective tooth and to the axis of rotation of the shaft, is smaller than a predetermined angle. The tips of the sawteeth may face forwardly in the direction of rotation of the shaft.