The dimensions of the holes respectively represent a single dimension of the inner surface. Dimensional tolerance is the most basic single tolerance, and its tolerance zone is one-dimensional. For example, a circular hole can be determined by its diameter.
The square hole must be divided into two single dimensions: length and width. The hole dimensions and tolerances in the length and width directions are given according to the inner surface.
When there is a matching relationship between parts, the relationship between hole and shaft is the relationship between inclusion and inclusion, that is, hole is the inclusion surface and shaft is the inclusion surface. Those without this matching relationship can be regarded as the length dimension.
Extended data:
According to the national standards, there are 13 types of base hole system, 59 types of common fit, 13 types of base shaft system and 47 types of common fit.
When choosing cooperation, the choice should be made in the order of priority and common use. When the priority cooperation can meet the requirements, in order to improve efficiency and shorten the design cycle, priority cooperation should be used as much as possible.
In the case of low precision requirements, rapid design can be carried out in small batch production by giving priority to cooperation. Process equivalence means that the machining difficulty of holes and shafts with the same fit is roughly the same.
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