Light projection area and some engineering properties for some grains (paddy rice and broad bean) were determined to assess their effectiveness on grain separation process. The main results in this study could be summarized as follows:- 1- It is possible to use light projection area directly for paddy rice and broad bean grains instead of mathematical surface area. 2- The hole dimensions of sieves were determined, in case of the round sieves, the diameters proper of holes were 8.00 and 14.5 mm. While, the distances between two holes were 6.00 and 10.7 mm) for rice and broad beans, respectively. In case of slot holes of sieves, the dimensions of hole were (8 x3.5 mm) and (14.5 x10.5 mm) while the distances between two holes were (7.5 x 2.5 mm) and (18.25 x 5.0 mm) for rice and broad bean, respectively. 3- The mean terminal velocity values were 20 and 75 m/s for paddy rice and broad bean, respectively. But, for the impurities of grains, the mean terminal velocity values were 5 and 15 m/s, respectively.   4- The friction angle (slope angle) of silo and hopper were 23 and 17 o for rice and broad bean, respectively using steel as material for silo and hopper. 5- The slop angleof sieves towardshorizontal plan was 5o for rice and 7o for broad bean.