On of the quality index that characterizes the threshing process is the percentage of unthreshed grain, i.e. threshing losses. This paper presents the effects of concave clearance; peripheral speed of cylinder (rotor) and material federate on threshing losses. The mathematical model that can describe the variation of threshing losses when concave clearance varies is represented by the equation (4); see also the Figures 1 and 2. Threshing losses decrease with peripheral speed of the rotor according to the equation (3); see Figure 3. There is a value of material throughput in order that threshing losses have a minimum; Figures 4 and 5.
