xvi Chapter 4 Datums........................................................................................ 109 Introduction. ...................................................................................................109 Datum Feature Symbol. ................................................................................110 Datum Features. .............................................................................................111 Datum Reference Frame................................................................................116 Datum Target Symbols..................................................................................126 Partial Datum Surface. ..................................................................................137 Coplanar Surface Datums.............................................................................138 Continuous Feature Symbol.........................................................................140 Datum Axis. ....................................................................................................140 Movable Datum Target Symbols and Datum Target Points. ...................148 Movable Datum Targets and Spherical Target Areas................................151 Datum Center Plane. .....................................................................................154 The Center of a Pattern of Features as the Datum Axis............................156 Applying a Translation Modifier to a Datum Feature Reference............156 Using a Contoured Surface as a Datum Feature. ......................................157 Chapter 5 Material Condition and Material Boundary. .................................183 Introduction. ...................................................................................................183 Material Condition and Material Boundary Symbols. .............................184 Functional Features........................................................................................185 Directly Toleranced Dimensioning..............................................................189 Limits of Size...................................................................................................189 Perfect Form Boundary. ................................................................................192 Regardless of Feature Size (RFS) and Regardless of Material Boundary (RMB). .....................................................................................194 Maximum Material Condition (MMC). ......................................................200 Least Material Condition (LMC)..................................................................205 Primary Datum Feature, RMB.....................................................................211 Secondary and Tertiary Datum Feature, RMB...........................................214 Datum Precedence and Material Boundary Condition............................214 Placing a Material Boundary Modifier in the Feature Control Frame......219 Material Condition and Boundary Analysis and Applications...............220 Material Boundary Calculation Examples. ................................................222 Chapter 6 Form Tolerances...........................................................................245 Introduction. ...................................................................................................245 Straightness of Line Elements. .....................................................................246 Derived Median Line Straightness..............................................................248 Straightness Applied on a Unit Basis..........................................................250 Straightness of a Flat Surface........................................................................252 Straightness of a Limited Length.................................................................253 Flatness Tolerance. .........................................................................................254 Circularity Tolerance. ....................................................................................262 Free State Variation. .......................................................................................266 Restrained Condition.....................................................................................267