It is proved that the critical-current density Jcof sintered YBa2Cu3O7-δsamples is decreased by 70% in the cutting surface layer and that this degradation is extended to a depth of around 0.1 mm. This is deduced form a critical-state model fit to field-dependent AC susceptibility data of two samples with different thicknesses cut from a pellet by an ordinary diamond saw. A spatial dependence of Jcin the critical-state model calculations is used to simulate the degradation. The local field-dependent Jcis also determined. © 1992.