Seeds of faba bean (Vicia faba , L) cv. Giza 40 , soybean (Glycine max , L) cv. Giza22 and chickpea (Cicer areitinum , L) cv. Giza1 were  separated manually just after physiological maturity . Collected seeds contained 6.2 , 5.5 and 5.9 % moisture content for faba bean , soybean and chick pea respectively prior to expose them  to mechanical damage by a device constructed and used to induce various levels of internal injuries. Different impact stresses were selected to induce invisible mechanical damage, whereas ,  six forces which is the combination between three different impact stresses and two seed positions were used .  Seed placed on the device either seed side face the falling weight (SFL) or embryonic axis face the falling weight (EAFL). Increasing impact stress caused seed to lose its vigourisity when faba bean, soybean and chick pea seeds stressed by F1 , F2 and F3. Seed position as well showed significant differences in all characters studied, whereas, seeds received falling load upon embryonic axis (EAFL) were more dramatically affected than seeds received falling load upon cotyledon area (SFL) of all studied legume species. Sensitivity of (EA) is not the only reason for vigourisity dramatic reduction occurred at  (EAFL) position, but also the increment of figured loads from F1, F2 and F3 in (N/mm2) for (SFL)  position to F1, F2 and F3 in (N / mm2) for (EAFL) position. Increasing contact area due to the seed shape caused figured impact stresses to be lower in faba bean seed, therefore, these lower forces enable the seed to survive the impact stress more than soybean and chick pea seeds . Not only the load used to induce internal damage affect the level of injury , but also part of seed to receive that load as well as the area that receive the load are factors to be paid more consideration when actual stresses to be figured . performance of (Fg) in diagnosing seed cracks in all studied species was the lowest , whereas , this method showed equal capability with other diagnosing method in diagnosing broken faba bean and soybean seeds. Visual, X-ray and tetrazolium had equal capability diagnosing seed cracks and broken areas of the three studied legume species. Highly negative correlation was found between broken seeds with vigour % as well as germination % of all studied legume species . Correlation analysis showed positive correlation between dead seeds %  and all broken seeds of all studied legume species. Differences in diagnosing methods (visual , X-ray and Tz ) capability  were narrowed showing close capability in predicting seed quality as well as in diagnosing  seeds internal damage.