Some main physical, mechanical and aerodynamic properties for Egyptian varieties of grains (Wheat, Giza 168 and Corn, Giza 10) were determined to know it's effective of some processing equipments. The main results in this study can be summarized as follows:- -          1) The relationship between frontal surface areas, thickness surface area and surrounded surface area were as a function of the product length, width and thickness, 2) In case of the round sieves, the diameter of holes was 3.75 and 7.0 mm while, the distance between two holes was of 5.5 and 10.34 mm at using of wheat and corn, respectively. In case of slot holes of sieves, the dimensions of hole was 8 x3 mm and 14x10.5 mm while the distance between two slot holes was 7.5 x 2.5 mm and 17.6 x 5.0 mm at using of  wheat and corn, respectively, 3) The terminal velocity was of 35 and 60 m/s of grains, the grains purity percentage was of 96 and 97 %, and grain losses were of 0.12 and 0.13 % for wheat and corn, respectively, 4) Tempering process of grains due to the moisture content was increased from 11 to 14% for wheat and from 12 to 14% for corn, respectively. This tempering process was required water quantity of 23.25 and 46.5 kg water/ ton grains for tempering of  wheat and corn, respectively, 5) The required force for milling process were of 59 and 265 N before tempering process, while it was 50 and 210 N after tempering process for wheat and corn, respectively. 6) The friction angle of silo and hopper was 19 and 16o for wheat and corn, respectively at using steel as material of silo and hopper, 7) The bulk density of grains was 1023 and 1495 kg/m3 for wheat and corn, respectively. These densities were gave storage capacity of silo 16.1 and 23.5 ton/ (2m diameter X 5 m height of silo), and 8) The study of physical, mechanical and aerodynamic properties is the very important at designed an agricultural machinery. It save the time, powered and labor then it less losses and gave a good grain quality impurities.