The comminution of metals (scraps) is carried out in order to obtain suitable fragment size distributions and/or to liberate the valuable components. In the case of thin-walled metals and metal scraps, respectively, shredders of the sing-hammer type are frequently used for the liberation and size reduction. The technically relevant equipment is introduced in this paper. Inside these shredders, the material is subject to complex stressing modes. On the basis of systematic investigations using a small-scale horizontal shaft shredder, four successive stages occurring during the process of the comminution of metal sheets are explained. (C) 2004 Elsevier B.V. All rights reserved.