【正文】 essive loose organization of metal, even a crack and peeling off the surface of the metal, declined to wear resistance. (B)The surface quality of the impact of fatigue strength Metal hand alternating loads of fatigue after the damage occurred in parts often Chilled layer below the surface and, therefore parts of the surface quality of fatigue very influential. 1. Surface roughness on the impact of fatigue strength In alternating load, the surface roughness of the Ausite easily lead to stress concentration, a fatigue crack, the higher the value of surface roughness, surface traces of Yu Shen Wen, Wen at the end of the radius smaller, antifatigue damage at the end of the more capacity Worse. 2. Residual stress, fatigue Cold Work hardening of the impact Residual stress on the impact of large parts fatigue. Surface layer of residual stress fatigue crack will expand and accelerate the fatigue damage the surface layer and the residual stress can prevent fatigue crack growth, delaying the formation of fatigue damage. (C)The surface quality of the corrosion resistance of the impact Parts of the corrosion resistance to a large extent depends on the surface roughness. The higher the value of surface roughness, Au Valley accumulate on the more corrosive substances. Corrosion resistance of the more worse. Surface layer of residual stress will produce stress corrosion cracking, lower parts of the wearresistance, and the residual stress is to prevent stress corrosion cracking. (D) The surface quality with quality Rough surface will affect the value of the size of the coordination with the surface quality. The gap with rough value will increase wear and tear, increased space, with the requirements of the destruction of nature. For Fit, the assembly part of the process of convex surfacecrowded peak times, the actual reduction of the surplus and reduce the support of the connection between the strength. Dimensioning The design of a machine includes many factors other than those of determining the loads and stresses and selecting the proper materials. Before construction or manufacture can begin, it is necessary to have plete assembly and detail drawings to convey all necessary information to the shop men. The designer frequently is called upon to check the drawings before they are sent to the shop. Much experience and familiarity with manufacturing processes are needed before one can bee conversant with all phases of production drawings. Drawings should be carefully checked to see that the dimensioning is done in a manner that will be most convenient and understandable to the production departments. It is obvious that a drawing should be made in such a way that it has one and only one interpretation. In particular, shop personnel should not be required to make trigonometric or other involved calculations before the production machines can be set up. Dimensioning is an involved subject and long experience is required for its mastery. Tolerances must be placed on the dimensions of a drawing to limit the permissible variations in size because it is impossible to manufacture a part exactly to a given dimension. Although small tolerances give higher quality work and a better operating mechanism, the cost of manufacture increases rapidly as the tolerances are reduced, as indicated by the typical curve of Fig . It is therefore important that the tolerances be specified at the largest values that the operating or functional considerations permit. Tolerances may be either unilateral or bilateral. In u