Copyright Goodheart-Willcox Co., Inc. 281 L E A R N I N G O B J E C T I V E S After studying this chapter, you will be able to: List and describe the geometric tolerances used to control orientation. Explain methods used to specify parallelism. Apply or interpret parallelism tolerances. Explain methods used to specify perpendicularity. Apply or interpret perpendicularity tolerances. Describe how to establish combination geometric tolerances. Explain methods used to specify angularity. Apply or interpret angularity tolerances. Identify and describe orientation tolerances specified at RFS, MMC, and zero geometric tolerance at MMC. T E C H N I C A L T E R M S angularity angularity tolerance multiple single-segment feature control frame orientation tolerances parallelism parallelism tolerance perpendicularity perpendicularity tolerance tangent plane Introduction T his chapter explains the concepts and techniques of dimensioning and tolerancing to control the orientation of features. Orientation tolerances control the angular relationships of features to one another. Orientation tolerances are used to control par- allelism, perpendicularity, and angularity. When size tolerances provided in directly toleranced dimensions and coordinate tolerancing do not give necessary control for the functional design and interchangeability of a product, then form and profile toler- ances can be specified. Size limits control a degree of form and parallelism. Positional tolerances control a certain amount of orientation. Therefore, the need for further form and orientation control should be evaluated before specifying form and orientation tolerances. Orientation Tolerances When specifying orientation tolerances, the tolerance zone is related to one or more datums. A relation to more than one datum should be considered if required to stabi- lize the tolerance zone in more than one direction. Orientation Tolerances C H A P T E R 7