EN ISO 2692:2021 PDF

Overview

EN ISO 2692:2021 - Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), Least material requirement (LMR) and Reciprocity requirement (RPR) (ISO 2692:2021) defines how to apply maximum- and least-material concepts and the reciprocity modifier to linear features of size. It is a GPS standard intended to control combined size and geometry where the two are interdependent (for example: assembly fits or minimum wall thickness). The document applies only to linear features of cylindrical type or two parallel opposite planes type.

Key topics

• Scope and applicability
  • Applies to features of size that are cylindrical or two parallel opposite planes.
  • Threaded features are not covered by specific rules in this standard (use with caution).
• Maximum Material Requirement (MMR)
  • Used to manage assemblability by accounting for worst‑case size and geometrical deviations (e.g., minimum assembly clearance when mating parts are at their maximum material size).
  • May be specified indirectly (via virtual size concepts) or by direct indication of the maximum material virtual size.
• Least Material Requirement (LMR)
  • Used to control functions such as minimum wall thickness or maximum slot width to protect part strength or function.
  • Also can be applied via indirect virtual size determination or by direct indication.
• Reciprocity Requirement (RPR)
  • Optional modifier used with MMR or LMR to allow enlargement of the size tolerance when the actual geometric deviation does not fully consume the maximum/least-material virtual condition.
• Modifiers and symbols
  • The 2021 edition adds provisions for direct indication of virtual sizes and introduces use of additional symbols (e.g., SZ, CZ, SIM) to support multi-feature and simultaneous requirements.
• Decision rules & GPS integration
  • Conforms with GPS terminology and is intended to work within the ISO/GPS framework and decision rules (e.g., ISO 8015, ISO 14253-1).

Applications

• Control of assemblies where size + geometric variation determine fit (MMR for assembly clearance).
• Ensuring minimum wall thickness or material‑related safety margins (LMR).
• Combining dimensional and geometrical controls into a single requirement to reflect actual functional intent.
• Drawing and specification practice for mechanical design, inspection callouts, and tolerance stack analysis.

Who uses this standard

• Mechanical designers and CAD engineers specifying tolerances
• Tolerancing and metrology specialists
• Manufacturing and quality engineers performing inspection and assembly verification
• Technical procurement and drawing reviewers in engineering and production environments

Related standards

• ISO 14638 (GPS matrix model)
• ISO 8015 (fundamental rules)
• ISO 14253-1 (decision rules for verification)
• ISO 286-1, ISO 14405-1, ISO 17450-1, ISO 17450-3 (related GPS and dimensional standards)

Keywords: EN ISO 2692:2021, MMR, LMR, RPR, geometrical tolerancing, GPS, maximum material requirement, least material requirement, virtual condition, assemblability, minimum wall thickness.