Friction of grain against construction materials depends on numerous factors, which the most important are: type of material, moisture content of grain, normal pressure, sliding path, orientation of grain against direction of sliding, air temperature and relative humidity and grain genus and variety. Coefficients of friction of various genera and varieties of grain differ sometimes distinctly. One of the reasons for this variability are differences in roughness and texture of grains surfaces. Grain moisture content is also considered one of the main reasons for variability in grain coefficient of friction. In general for cereal grains, coefficient of friction increases with an increase in moisture content, particularly above 13%. However for some grains minimum was observed for moisture contents below 15%.