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未注公差尺寸在产品零件图的尺寸数量上比重较大。一般对于精度要求较低或不须配合部位的尺寸大多数采用这个形式来表达。它使图面清晰,重点突出,有利于产品零件主要部位精度的明确。但由于对未注公差值和公差偏差在有关资料中没有确切的说明,以致造成生产应用上的混乱。按1979年新国标规定,未注公差一般在IT12～IT18范围内(相当于旧国标GB7～GB12),其中冲压件的未注公差则在IT13～IT15范围内(相当于GB7～GB10)。
Not note tolerance size in the number of parts on the size of the larger proportion. The general requirements for the accuracy of the lower part of the size or do not need to use most of this form to express. It makes the picture clear and focused, which is good for the accuracy of the main parts of the product parts. However, due to the unmarked tolerances and tolerance deviations in the relevant information is not precise, resulting in confusion in the production and application. According to the provisions of the new national standard in 1979, the unmarked tolerances are generally within the range of IT12 ~ IT18 (equivalent to the old national standard GB7 ~ GB12). The unmarked tolerances of the stamping parts are within the range of IT13 ~ IT15 (equivalent to GB7 ~ GB10).