الفهرس 
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Abstract
The objective of this investigation is to reach the optimum conditions of : Operation efficiency; grain quality; threshing capacity; proper lengths of straw flakes (tibn); Minimum power and; least costs for threshing and tenderizing straw. That while applying the two flows of threshing tangential or axial one , which help to use the thresher more than one season and several crops. All measured treatments will estimated under the circumstances cylinder speed, cylinder concave clearance, crop moisture content and different modifications of the threshing chamber. The machine performance was evaluated by determining the following measurements: Unthreshed grains; damaged grains; Machine capacity; straw flakes (tibn) lengths and power required. These measurements were determined under the following factors: 1Different cylinder speeds, 21.3, 25, 28.5, 33.1 and 37.4 m/sec.; 2 Different crop moisture contents, 19.2, 16.5 and 13.7 % ; 3 Different levels of cylinder concave clearance, 1.5/0.5, 2.5/1 and 3.5/1.5 (front/rear) cm; 4 Enlarging the feed opening width in axial flow from 50 to 70 cm; 5 Assembling four sweepers among separation rows part in axial flows; 6 Sharpening all knives in both two flows; and 7 Open the concave end in tangential system. Results can be summarized as following: 1 Closed tangential system achieve the best result in tenderizing straw (<2.5cm), least cost to threshing, tenderizing straw (8.0L.E/Ardab) and minimum losses (0.0L.E of unthreshed grains); 2 Opened tangential flow achieve the maximum capacity (35.5kg/min), least cost to threshing only (4.3L.E), but give the maximum losses than another flows (33.8L.E/Ardab); 3 Axial flow with sharpen knives is nearest to close tangential one; 4 Possibility of tenderizing the straw with both axial and close tangential flow; 5 Using drum speed 37.4 m/sec.; 6 Threshing wheat at M.C 13.7%, d.b; 7 Using clearance 3.5/1.5, front/rear; and 8 Enlarging the feed opening width in axial system from 50 to 70 cm to increase input capacity.