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【正文】 tances. 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 unilateral dimensioning, one tolerance is zero, and all the variations are given by the other tolerance. In bilateral dimensioning, a mean dimension is used which extends to the midpoint of the tolerance zone with equal plus and minus variations extending each way from this dimension. The development of production processes for largevolume manufacture at low cost has been largely dependent upon interchangeability of ponent parts. Thus the designer must determine both the proper tolerances for the individual parts, The manner of placing tolerances on drawings depends somewhat on the kind of product or type of manufacturing process. If the tolerance on a dimension is not specifically stated, the drawing should contain a blanket note which gives the value of the tolerance for such dimensions. However, some panies do not use blanket notes on the supposition that if each dimension is considered individually, wider tolerance than those called for in the note could probably be specified. In any event it is very important that a drawing be free from ambiguities and be subject only to a single interpretation. Dimension and Tolerance In dimensioning a drawing, the numbers placed in the dimension lines represent dimension that are only approximate and do not repres
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