![]() As the size of the feature departs from MMC toward LMC, a bonus toler- ance is gained in the exact amount of such departure. The MMC modifier (circle M) is not to be confused with the MMC size of a feature as shown in Fig. The MMC size of a feature is the largest shaft and the smallest hole. Symbols, Terms, and Rules Symbols, Terms, and Rules 23TABLE 3-1 Material Condition SymbolsMaterial condition modifier Abbreviation SymbolRegardless of feature size RFS NoneMaximum material condition MMCLeast material condition LMC Ml Ll Where the Maximum Material Condition Modifier (circle M) is specifiedto modify a size feature in a feature control frame, the following two require-ments apply: The specified tolerance applies at the Maximum Material Condition (MMC) size of a feature. Any use is subject to the Terms of Use as given at the website. Material condition modifiers are explained in more detail in Chapter 7.Downloaded from Digital Engineering Library McGraw-Hill (Copyright © 2006 The McGraw-Hill Companies. Geometric tolerances specified at RFS are often used when tolerancing high speed, rotating parts, or when symmetrical relationships are required. A tolerance specified at RFS is only the tolerance specified in the feature control frame, and no bonus tolerance is added. If no material condition symbol is specified for the tolerance or datum reference, the feature automat- ically applies at RFS, which means that the tolerance is the same, no matter what size the feature has been produced within its limits of size. This symbol is no longer used because RFS, in the current standard, is the default material condition modifier. If a size feature has a geometric tolerance or if it is used as a datum, then the tolerance or datum applies at one of these material conditions (Table 3-1): Regardless of feature size Maximum material condition Least material condition In previous revisions of the geometric tolerancing standard, the symbol for RFS was a circle S. Perpendicularity RefinedFigure 3-6 Composite, two single segments, and refined feature control frames.Material conditions One of the major advantages of using GD
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