ISO/TC 213/WG 18 - Geometrical tolerancing

This document defines the maximum material requirement (MMR), the least material requirement (LMR) and the reciprocity requirement (RPR). These requirements can only be applied to linear features of size of cylindrical type or two parallel opposite planes type. These requirements are often used to control specific functions of workpieces where size and geometry are interdependent, for example to fulfil the functions “assembly of parts” (for MMR) or “minimum wall thickness” (for LMR). However, the MMR and LMR can also be used to fulfil other functional design requirements.

This document gives rules for definition and interpretation of general geometrical specifications and general size specifications defined according to ISO 8015:2011, 5.12. General specifications defined in other standards, and the link to these standards, are not covered by this document. The general geometrical specifications and general size (linear or angular) specifications defined in this document apply only to integral features (including features of size). These specifications do not apply to derived features or integral lines (see ISO 17450-1 for the definitions of integral features and derived features). Dimensions other than linear or angular sizes (see ISO 14405-2) are not covered by this document.

This document establishes complementary rules to ISO 1101 to be applied to pattern specifications and defines rules to combine individual specifications, for geometrical specifications e.g. using the symbols POSITION, SYMMETRY, LINE PROFILE and SURFACE PROFILE, as well as STRAIGHTNESS (in the case where the toleranced features are nominally coaxial) and FLATNESS (in the case where the toleranced features are nominally coplanar) as listed in Annex C. These rules apply when a set of tolerance zones are grouped together with location or orientation constraints, through the use of the CZ, CZR or SIM modifiers. This document does not cover the use of the pattern specifications when the least and maximum material requirement is applied (see ISO 2692). This document does not cover the establishment of common datum (see ISO 5459) based on pattern features.

ISO 1660:2017 gives the rules for geometrical specifications of integral and derived features, using the line profile and surface profile characteristic symbols as defined in ISO 1101.

ISO 1101:2017 defines the symbol language for geometrical specification of workpieces and the rules for its interpretation. It provides the foundation for geometrical specification. The illustrations in this document are intended to illustrate how a specification can be fully indicated with visible annotation (including e.g. TEDs). NOTE 1 Other International Standards referenced in Clause 2 and in Tables 3 and 4 provide more detailed information on geometrical tolerancing. NOTE 2 This document gives rules for explicit and direct indications of geometrical specifications. Alternatively, the same specifications can be indicated indirectly in accordance with ISO 16792 by attaching them to a 3D CAD model. In this case, it is possible that some elements of the specification are available through a query function or other interrogation of information on the model instead of being indicated using visible annotation

ISO 10579:2010 gives rules for dimensioning and tolerancing non-rigid parts where restraining of features is required during verification of dimensions and tolerances specified on a drawing.

ISO 2692:2014 defines the maximum material requirement, the least material requirement and the reciprocity requirement. These requirements can only be applied to features of size. These requirements are used to control specific functions of workpieces where size and geometry are interdependent, e.g. to fulfil the functions "assembly of parts" (for maximum material requirement) or "minimum wall thickness" (for least material requirement). However, the maximum material requirement and least material requirement are also used to fulfil other functional design requirements. Considering this interdependence between size and geometry, the principle of independency defined in ISO 8015 does not apply when the maximum material requirement, least material requirement, or reciprocity requirement, are used.