270 Machine Trades Print Reading Copyright Goodheart-Willcox Co., Inc. Drawing Interpretation .015 diameter tolerance zone Goodheart-Willcox Publisher Figure 15-18. Specifying derived median line straightness. Drawing Interpretation .003 tolerance zone Goodheart-Willcox Publisher Figure 15-19. Specifying a flatness tolerance for a surface. Low limit High limit .005 flatness tolerance zone Goodheart-Willcox Publisher Figure 15-20. Specifying a flatness tolerance to control a surface. The part must also be within the specified size tolerance when produced.