The study aims to modify and evaluate the performance of the local crushing machine used in the Egyptian poultry farms for crushing and grinding soybean and maize grains. The effect of some parameters such as screen opening sizes (6, 9 and 14 mm.), feeding rates (250, 400, 500 and 700 kg/h), the number of hummers (45, 60 and 90) and flywheel diameters, (200, 350, 450 and 600 mm) on the fineness degree, (%), power, (kW), and energy requirements (kW.h/Mg) were investigated. The optimum operating conditions of the modified hummer mill were obtained at the screen opening sizes of 6 and 9 mm for soybean and maize grains respectively, feeding rate of 550 kg/h, number of hummers of 90, and the flywheel diameter of 450mm. The results also showed that changing the size of the hammer mill electric motor from 7.5 to 11 kW gave high performance and safe operation with different number of hammers and flywheel diameter for all treatments.