Wheat and barley thresher was improved for its threshing capacity and suitability of operation and performance evaluation was done on wheat and barley crops. The size of previous wheat and barley thresher was increased and the feeding system that blows the dust outward to the operator was improved. The major components of the improved wheat and barley thresher include threshing unit, cleaning unit, feeding table, straw and chaff discharging unit and grain discharging unit. It was tested to

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... h, separate and clean the wheat and barley seeds. The results showed that the machine had the maximum threshing capacity of 538 and 424 Kg/hr at feeding rate of 1000 Kg/hr and drum speed of 1100 rpm with grain straw ratio of 1:0.96 and 1:1.44 of wheat and barley crops respectively. The maximum threshing and cleaning efficiency of 98.95 and 99.93 %, 98.13 and 97.91 % and grain breakage of 0.52 and 1.06 % at above combination of 1100 rpm drum speed and 1000 Kg/hr feed rate for wheat and barley crops respectively. The maximum fuel consumption recorded were 0.73 and 0.60 liters per hour at moisture content of 12.5 and 11 % (d.b) at the combination of 1000 Kg/hr feed rate and 1100 rpm drum speed for wheat and barley respectively. The successful improvement of this machine is expected to reduce drudgery associated with the traditional method of threshing wheat and barley, and therefore increase productivity of farmers by reducing postharvest losses.