Abstract: A cylindrical classifier includes a first rotating cylinder having a surface composed of parallel separator rods or tubes that extend along the length of the cylinder. The tubes or rods are spaced from each other to prevent oversized objects from passing between them. Material to be classified is fed to the interior of the cylinder. As the cylinder rotates, objects of the desired size and smaller objects pass between the spaced separator rods and exit the cylinder. The first cylinder is surrounded by a second coaxial cylinder so that there is a space between the first and second cylinders. The outer cylinder has a separating screen which prevents objects of a desired size from passing through.