Pressed steel sheets, in this case compacted vehicle bodies represent the structure diversity of the non-homogeneous material. There is necessity to determine the shear strength for the development of the construction of new processing equipment (cutting) of steel sheets. To calculate the shear strength it is necessary to know the ultimate firmness of the material. For homogeneous materials this parameter is normally available in the tables. The article discusses the experimental detection of boundary strength of pressed metal of vehicle bodies. To gain some relevant statistical evaluation the samples of the car body have been divided into three groups according to the engine capacity. The experiment was evaluated by the following statistical methods, analysis of variance using the AIC criterion and Grubbs test for outliers. According to the analysis of the measured parameters the resulting mathematical model, which is used for determination of optimal values of boundary strength, has been established. The resulting mathematical model can be used to determine the boundary strength, which serves as an input parameter for the calculation of shear strength required for the development of new equipment designed for the processing of scrap metal, with cutting.