295 Copyright Goodheart-Willcox Co., Inc. CHAPTER 8 Position Tolerancing Fundamentals Technical Terms actual minimum material envelope additional tolerance axis method bidirectional position tolerance boundary method fi xed fastener condition fl oating fastener condition paper gaging position tolerance position tolerance zone projected tolerance zone surface method true position Objectives Information in this chapter will enable you to: → Complete feature control frames for position tolerances, properly using the diameter symbol, material condition modifi ers, and datum feature references. → Sketch the proper location and shape for position tolerance zones. → Describe the effect of MMC, LMC, or RFS applicability on a position tolerance. → Provide examples that prove the validity of the MMC concept as it applies to position tolerances. → Calculate position tolerances for simple fi xed and fl oating fastener conditions. → Calculate the allowable additional (bonus) tolerance for a produced part on which a position tolerance is specifi ed at MMC. → Use calculation techniques to verify whether produced hole locations meet specifi ed drawing tolerances. → Cite advantages of position tolerances when compared to coordinate hole location tolerances. Models and drawings of production parts include tolerances that defi ne the acceptable amount of variation on features. There must be an allowable variation on all aspects of the part geometry, including the locations for features of size. As an example, the required location for a hole must include a tolerance. One method for defi ning location tolerances on holes and other features of size is to apply a posi- tion tolerance. A position tolerance specifi es the allowable variation of location relative to a specifi ed basic position. Models and drawings that provide complete product defi nition must specify the acceptable amount of variation on sizes and locations because it is not possible to produce perfect parts. This chapter describes how to use position tolerances for specifi cation of allowable location variation. Introduction