iii
CONTENTS
Foreword .............................................................................................................................................................................. vi
Committee Roster ................................................................................................................................................................ viii
Correspondence With the Y14 Committee ...................................................................................................................... ix
Section 1 Scope, Definitions, and General Dimensioning ...................................................................................... 1
1.1 Scope ................................................................................................................................................................ 1
1.2 References ....................................................................................................................................................... 1
1.3 Definitions ...................................................................................................................................................... 2
1.4 Fundamental Rules ........................................................................................................................................ 7
1.5 Units of Measure ............................................................................................................................................ 8
1.6 Types of Dimensioning ................................................................................................................................. 9
1.7 Application of Dimensions .......................................................................................................................... 10
1.8 Dimensioning Features ................................................................................................................................. 13
1.9 Location of Features ...................................................................................................................................... 20
Section 2 General Tolerancing and Related Principles .......................................................................................... 24
2.1 General ............................................................................................................................................................ 24
2.2 Direct Tolerancing Methods ......................................................................................................................... 24
2.3 Tolerance Expression ..................................................................................................................................... 25
2.4 Interpretation of Limits ................................................................................................................................. 26
2.5 Single Limits ................................................................................................................................................... 26
2.6 Tolerance Accumulation ............................................................................................................................... 26
2.7 Limits of Size .................................................................................................................................................... 27
2.8 Applicability of Modifiers on Geometric Tolerance Values and Datum Feature References ............. 29
2.9 Screw Threads ................................................................................................................................................ 31
2.10 Gears and Splines .......................................................................................................................................... 31
2.11 Boundary Conditions .................................................................................................................................... 31
2.12 Angular Surfaces ........................................................................................................................................... 31
2.13 Conical Tapers ................................................................................................................................................ 35
2.14 Flat Tapers ....................................................................................................................................................... 35
2.15 Radius .............................................................................................................................................................. 36
2.16 Tangent Plane ................................................................................................................................................. 36
2.17 Statistical Tolerancing ................................................................................................................................... 36
Section 3 Symbology .............................................................................................................................................. 38
3.1 General ............................................................................................................................................................ 38
3.2 Use of Notes to Supplement Symbols ........................................................................................................ 38
3.3 Symbol Construction ..................................................................................................................................... 38
3.4 Feature Control Frame Symbols .................................................................................................................. 44
3.5 Feature Control Frame Placement ............................................................................................................... 46
3.6 Definition of the Tolerance Zone ................................................................................................................. 46
3.7 Tabulated Tolerances ..................................................................................................................................... 46
Section 4 Datum Reference Frames ........................................................................................................................ 48
4.1 General ............................................................................................................................................................ 48
4.2 Degrees of Freedom ....................................................................................................................................... 48
4.3 Degrees of Freedom Constrained by Primary Datum Features
Regardless of Material Boundary ............................................................................................................ 48
4.4 Constraining Degrees of Freedom of a Part ............................................................................................... 48
4.5 Datum Feature Simulator ............................................................................................................................. 53
4.6 Theoretical and Physical Application of Datum Feature Simulators ..................................................... 53
4.7 Datum Reference Frame ............................................................................................................................... 53
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