Ethiopia has a highly diversified agro- ecological condition, which makes possible the production of a wide range of agricultural products. Threshing of cereal crops by hand or manually or simple tools is a time consuming and a tedious process and leads to high post harvesting loss. The drudgery involved in the manual threshing or shelling of the cereal crops has discouraged the mass production and commercialization of the cereal crop and this necessitates the development and evaluation of a motorized operated crop threshing or shelling machine using impact method. In order to help small scale agriculture, increase its contribution ensure food security, threshing operation and its subsequent loss followed is among points requiring proper attention and that gently account about 30% of cereal crop loss in Ethiopia. In rural area like in Ethiopia is done by traditional methods. This method is the time wasting, energy supping and often the grain is broken or damage. In developing world, crop threshing is done by various PTO operated machines, but in rural areas the farmers who lacks in financial condition cannot afford this machine. To overcome this problem, this research deals with adaptation, design and fabricate a multipurpose threshing, for threshing of variety of cereal crops. This machine was constructed to thresh cereal crops and separate the cobs or chaffs from the grains. The thresher was constructed from locally available materials made from mild steel and its operation does not require any special skills. The test was carried out at speed 450, 540, and 730 rpm, 1100 and 1440 rpm, 1200 and 1440 rpm for maize, wheat and Teff respectively and the moisture contents of 15,2, 10 and 8 %(wb) for maize, wheat and Teff respectively. Its threshing efficiency around 99.98 for maize%,99.9% for wheat, and 100% for Teff and the threshing capacity 2500kg/hr- 3000kg/hr, 750.53kh/hr and 280kg/hr for maize, wheat and Teff respectively and breakage is very insignificant, as well as losses for all. The machine, threshing action are done by using replaceable drum, it depends on the type of crop, for maize twisted rasp bar type drum but for wheat and Teff raspbar drum. It is also capable of reducing time wastage, reduction of breakage of the grain, increase the efficiency of threshing, separation of stalk from the grain and also increase the winnowing action during threshing, in order to increase the quality of the threshing crops. The results of the analysis showed that increase in the speed of the threshing unit increases the threshing and cleaning capacities of the thresher. However, breakage of the threshed crops seeds also increases with an increase in the speed of the threshing unit. When the moisture content of the crops seeds was increased from 13% -18% there was drastic reduction in the amount of broken seeds from 0.3 to 0.15 % for maize. The thresher performed satisfactorily and is suitable for domestic and commercial threshing of cereal crop seeds.