ISO 2692:2021 pdf download – Geometrical product specifications (GPS) — Geometrical tolerancing — Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR).
3.12 maximum material requirement MMR requirement for a feature of linear size (3.2), defining a geometrical feature of the same type and of perfect form, with a given value for the intrinsic characteristic (dimension) equal to the maximum material virtual size (3.8), which limits the non-ideal feature on the outside of the material Note 1 to entry: MMR is used to control the assemblability of a workpiece. Note 2 to entry: See also 4.2. 3.13 least material requirement LMR requirement for a feature of linear size (3.2), defining a geometrical feature of the same type and of perfect form, with a given value for the intrinsic characteristic (dimension) equal to the least material virtual size (3.10), which limits the non-ideal feature on the inside of the material Note 1 to entry: LMR is used, for example, to control the minimum wall thickness between two symmetrical or coaxially located similar features of size. Note 2 to entry: See also 4.3. 3.14 reciprocity requirement RPR additional requirement for a feature of linear size (3.2) indicated in addition to the maximum material requirement (3.12) or the least material requirement (3.13) to indicate that the size tolerance is increased by the difference between the geometrical tolerance and the actual geometrical deviation 3.15 external feature of linear size feature of linear size (3.2) where vectors normal to the surface are directed outward from the material in a direction opposite to the median feature Note 1 to entry: The cylindrical surface of a shaft is considered to be an external feature of linear size. Note 2 to entry: See Figure 1.
4 Maximum material requirement (MMR) and least material requirement (LMR) 4.1 General 4.1.1 MMVS or LMVS specification The MMR and the LMR can be applied to a set of one or more feature(s) of size as toleranced feature(s), datum(s) or both. The MMVS or the LMVS shall be specified by one of the two following options: a) An MMR without direct indication of MMVS or an LMR without direct indication of LMVS but with a size specification for the considered feature. This option is referred to as indirect determination of virtual size in this document. b) An MMR with direct indication of MMVS between square brackets in the tolerance indicator or an LMR with direct indication of LMVS between square brackets in the tolerance indicator as explained in this document. This option is referred to as direct indication of virtual size. A geometrical specification with MMR or LMR shall be indicated as applying to a derived feature. However, the toleranced feature considered in the rules of this document is the corresponding integral feature. The rules in this document shall not be applied to threaded features, even if threaded features are often considered as cylindrical features in GPS standards. The possible combinations of geometrical characteristic symbols and MMR or LMR are illustrated in Annex D.