Modifiers on geometric tolerances

RFS, MMC, and LMC may be applied to geometric tolerance values on features of size. See Figs. 7-34 and 8-24. RMB, MMB, and LMB may be applied to datum feature references. Rule #2 RFS applies, with respect to the individual tolerance, and RMB applies, with respect to the individual datum feature reference, where no modifying symbol is specified. MMC, LMC, MMB, or LMB shall be specified on the drawing where it is required.

NOTES: (1) The following paragraphs describe the principles based on an axis interpretation for RFS, MMC, and LMC. In certain cases of surface deviation of the feature, the tolerance in terms of the feature axis or feature center plane may not be exactly equivalent to the tolerance in terms of the surface limited by a boundary. In such cases, the surface interpretation shall take precedence. See para. 7.3.3.1(a) and Fig. 7-6.

(2) Circular runout, total runout, concentricity, profile of a line, profile of a surface, circularity, cylindricity, and symmetry tolerances are applicable only on an RFS basis and cannot be modified to MMC or LMC.

  1. Effect of RFS
  2. Effect of MMC
  3. Effect of zero tolerance at MMC
  4. Effect of LMC
  5. Effect of zero tolerance at LMC

Effect of RFS

Where a geometric tolerance is applied on an RFS basis, the specified tolerance is independent of the size of the considered feature of size. The tolerance is limited to the specified value regardless of the size of the unrelated actual mating envelope.

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