306 Geometric Dimensioning and Tolerancing Copyright Goodheart-Willcox Co., Inc. Placing the MMC material condition symbol after the geometric tolerance in the feature control frame means that the geometric tolerance is held at the MMC size, and then the geometric tolerance may increase equal to the amount of departure from MMC. Another application is zero geometric tolerance at MMC. This is done by specify- ing zero for the geometric tolerance in the feature control frame and using the MMC material condition symbol. This means that at the MMC size, the feature must be in perfect orientation with respect to the specified datum. As the actual size departs from MMC, the geometric tolerance increases equal to the amount of departure. This is done to establish perfect orientation at MMC to control the relationship between fea- tures. Example 7-23 shows applications of RFS, MMC, and zero geometric tolerance at MMC. The idea behind using zero geometric tolerance at MMC is to allow more size tolerance. In Example 7-23, with zero geometric tolerance at MMC applied, the size tolerance is increased to 19.7–20.2 as shown. Zero orientation tolerance at MMC can be used for parallelism, perpendicularity, or angularity. A B C Optional feature control frames Orthographic views 19.8 19.7 0.1 0.1 0 19.9 19.8 0.1 0.2 0.1 20.0 19.9 0.1 0.3 0.2 20.1 20.0 0.1 0.4 0.3 20.2 20.1 0.1 0.5 0.4 20.2 0.5 19.8–20.2 Possible Produced Sizes 19.7–20.2 Possible Produced Sizes Geometric Tolerances Based on the Optional Feature Control Frames A. RFS B. MMC C. Zero at MMC MMC LMC Goodheart-Willcox Publisher Example 7-23. Applications of orientation tolerances at RFS, MMC, and zero tolerance at MMC.