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从上一讲所讨论的位置公差可见,要讨论位置公差就离不开基准问题,实际生产中无论是加工、检验或装配也都存在着基准选择的问题。因此,我们在这一讲中,有必要对基准的一些基本概念及生产中的应用问题,再做进一步讨论。一、基准与基准要素零件上某一要素的位置,是相对于该零件上另外所指定的要素而言。如图1所示零件的上平面为一平行面,ф20H7孔的轴心线为一垂直线,都是相对于下平面A而言。离开平面A,也就谈不到什么平行或垂直位置。零件
From the previous discussion of the location of the tolerance can be seen, to discuss the position tolerance can not be separated from the benchmark problem, the actual production of both processing, testing or assembly there is also the issue of benchmarking. Therefore, in this speech, we need to further discuss some of the basic concepts of the benchmark as well as application problems in production. First, the benchmark and benchmark elements of a component of the position, is relative to the other components on the designated elements. As shown in Figure 1 parts of the plane as a parallel plane, ф20H7 hole axis for a vertical line, are relative to the plane A in terms of the next. Leaving plane A, there is no parallel or vertical position. Components