A grinder for grinding relatively loose materials includes a reducing unit and a screen arrangement. The arcuate screen defines a plurality of tracks of apertures that extend in a cutting direction of the cutters. In some cases, only one respective cutter passes over each track and each cutter passes over only the respective one of the tracks. The width of a cutter may be greater than a width of the apertures of a track. The apertures of the screen arrangement may form chevron patterns. The screens may be clamped to a frame by coupling members extending through notches in the screen.