Hands for watches ; upper and lower deviations for holes and shafts 手表的指针.孔和轴的上下偏差
2.
It is the first time to define the tolerance with upper deviation smaller than lower deviation as virtual tolerance which is given in this paper as well 摘要把上偏差小于下偏差的公差定义为虚公差，探讨了虚公差存在的理论基础及其意义，从而丰富了公差的内涵而发展为广义公差，更适合计算机辅助公差设计。
