Tolerance and Fitting - General Standard Tolerance and Fundamental Deviation
公差與配合
總論 標準公差與基本偏差
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.
Figure 1 Schematic Diagram for Tolerance and Fitting
Figure 2 Tolerance Range Diagram
11. Standard tolerance: any tolerance listed in the table of this standard and used for determining the size of tolerance range.
12. Tolerance unit: the basic unit for standard tolerance calculation, also the function of basic size.
13. Tolerance grade: the grade determining the size accuracy.
The tolerance belonging to the same tolerance grade; all basic sizes, though with different numerical values, are deemed to have equal accuracy.
14. Basic deviation: the upper deviation or lower deviation listed in the table of this standard and used for determining the relative position of tolerance range in relation to zero line; generally, it is taken as the deviation close to zero line (Figure 3).
Figure 3 Basic Deviation Series
15. Fitting: relationship between the mutually fitted hole and shaft tolerance ranges of the same basic size.
16. Clearance or interference: the algebraic difference of hole size subtracting the fitted shaft size. The positive difference is clearance while the negative one is interference.
17. Clearance fitting: the fitting equipped with clearance (including the zero minimum clearance). In this case, the hole tolerance range is above the shaft tolerance range (Figure 4).
Figure 4 Clearance Fitting
18. Interference fitting: the fitting equipped with interference (including the zero minimum interference). In this case, the hole tolerance range is below the shaft tolerance range (Figure 5).
Figure 5 Interference Fitting
19. Transition fitting: the fitting with potential clearance or interference. In this case, the hole tolerance range is overlapped with shaft tolerance range (Figure 6).
20. Minimum clearance: the algebraic difference of the minimum limit size of hole subtracting the maximum limit size of shaft for clearance fitting (Figure 4).
Figure 6 Transition Fitting
21. Maximum clearance: the algebraic difference of the maximum limit size of hole subtracting the minimum limit size of shaft for clearance fitting or transition fitting (Figure 4 and Figure 6).
22. Minimum interference: the algebraic difference of the maximum limit size of hole subtracting the minimum limit size of shaft for interference fitting (Figure 5).
23. Maximum interference: the algebraic difference of the minimum limit size of hole subtracting the maximum limit size of shaft for interference fitting or transition fitting (Figure 5 and Figure 6).
24. Fitting tolerance: the permissible variation of clearance or interference.
The fitting tolerance equals to the absolute value of algebraic difference between maximum clearance and minimum clearance for clearance fitting, the absolute value of algebraic difference between minimum interference and maximum interference for interference fitting, and the absolute value of algebraic difference between maximum clearance and maximum interference for transition fitting.
Fitting tolerance also equals to the sum of tolerances of mutually fitted hole and shaft.
25. Basic hole system: a system where the hole tolerance range with certain basic deviation is fitted with shaft tolerance ranges with different basic deviations.
The hole of basic hole system is datum hole; for the datum hole specified in this standard, its lower deviation is 0 (Figure 7).
26. Basic shaft system: a system where the shaft tolerance range with certain basic deviation is fitted with hole tolerance ranges with different basic deviations.
The shaft of basic shaft system is datum shaft; for the datum shaft specified in this standard, its upper deviation is 0 (Figure 7).
Figure 7 Basic Hole System and Basic Shaft System
27. Maximum material condition (hereinafter referred to as MMC) and maximum material size: the condition where the hole or shaft is provided with the maximum permissible material quantity is referred to as maximum material condition (MMC). The limit size under this condition is referred to as maximum material size, and is a general term for the minimum limit size of hole and maximum limit size of shaft.
28. Least material condition (hereinafter referred to as LMC) and least material size: the condition where the hole or shaft is provided with the least permissible material quantity is referred to as least material condition (LMC). The limit size under this condition is referred to as least material size, and is a general term for the maximum limit size of hole and minimum limit size of shaft.
29. Mating size of hole or shaft: the size of the maximum ideal inscribed shaft in the actual hole on the total length of fitting surface is referred to as the mating size of hole; the size of the minimum ideal circumscribed hole of the actual shaft is referred to as the mating size of shaft.
Figure 8 Mating Size of Hole or Shaft
II. Basic Requirements
30. Basic size segment: basic size segments are detailed in Table 1.
I. Terms and Definitions
II. Basic Requirements
Appendix
