This standard is applicable to the dimensional tolerance of cylindrical surface and other surface or structure as well as their fitting.
I. Terms and Definitions
1. Size: the number representing the length in specific unit.
2. Hole: mainly refer to the internal surface of cylinder, also including the part determined by single size in other internal surfaces.
3. Shaft: mainly refer to the external surface of cylinder, also including the part determined by single size in other external surfaces.
4. Basic size: the size given in design.
5. Actual size: the measured size.
6. Limit size: two limit values of permissible size variation, which is determined with basic size as base number.
The larger one of two limit values is referred to as maximum limit size while the smaller one is referred to as minimum limit size.
7. Size deviation (hereinafter referred to as deviation): the algebraic difference of certain size subtracting its basic size.
The algebraic difference of maximum limit size subtracting its basic size is referred to as upper deviation, while that of minimum limit size subtracting its basic size is referred to as lower deviation; the upper deviation and lower deviation are collectively referred to limit deviation. The algebraic difference of actual size subtracting its basic size is referred to as actual deviation. The deviation may be positive, negative or zero value.
8. Size tolerance (hereinafter referred to as tolerance): the permissible size variation.
The tolerance is equal to the absolute value of the algebraic difference between the maximum limit size and the minimum limit size and also equal to the absolute value of the algebraic difference between the upper deviation and the lower deviation.
9. Zero line: a datum straight line determining the deviation in tolerance and fitting illustration (hereinafter referred to as tolerance range diagram), namely the zero deviation line. Generally, zero line represents the basic size.
10. Size tolerance range (hereinafter referred to as tolerance range): a zone limited by two straight lines respectively representing the upper/lower deviation in tolerance range diagram.
Figure 1 specifies above terms and their interrelationship. For the purpose of simplification, it is generally represented by tolerance range diagram (Figure 2) in actual use.
