What is ISO 21920‑3 – GPS specification operators about?
ISO 21920‑3 is an International Standard that discusses geometrical product specifications (GPS). Geometrical product specification is the international symbol language used to express tolerances in technical drawings.
ISO 21920‑3 is the third part of the multi-series and specifies the complete specification operator for surface texture by profile methods. The fundamental rules of ISO GPS given in ISO 8015 apply to ISO 21920‑3 and the default decision rules given in ISO 14253-1 apply to the specifications made in accordance with ISO 21920‑3, unless otherwise indicated.
Throughout ISO 21920‑3, parameters are written as abbreviated terms with lower-case suffixes (as in Rq) which are used in product documentation, drawings, and datasheets. The parameters in lower case are used in product documentation, drawings, and datasheets.
Who is ISO 21920‑3 – GPS specification operators for?
ISO 21920‑3 on GPS specification operators is useful for:
- Mechanical engineers, design engineers, and engineering designers in aerospace, defence, automotive, rail, nuclear, and medical devices sectors
- Manufacturing and production engineers
- Metrologists
- Quality control teams
- Independent design consultancies and design agencies
- Research and development facilities
- Scientific laboratories
Why should you use ISO 21920‑3 – GPS specification operators?
Geometrical product specification is the system used to define the geometrical requirements of workpieces in engineering specifications, and the requirements for their verification. The concept of GPS is applicable at several steps in the development of a product such as design, manufacturing, metrology, quality assurance, conformity assessment, delivery, installation, use and final disposal.
ISO 21920‑3 specifies the specification operators which consists of all the operators required for an unambiguous specification. It consists of an ordered full set of unambiguous specification operations in an unambiguous order. ISO 21920‑3 helps you to ensure optimum functioning of each product and you will be able to overcome problems in geometrical product specification and verification for all players of the product development process (design, manufacturing, and inspection/verification).
What’s changed since the last update?
BS EN ISO 21920‑3:2022 supersedes BS EN ISO 4288:1998, which is withdrawn. BS EN ISO 21920‑3:2022 includes some technical changes with respect to BS EN ISO 4288:1998. These include:
- No distinction between periodic and non-periodic profiles
- The basis for defaults is the drawing indication
- The maximum tolerance acceptance rule is the default tolerance acceptance rule
- For the determination of the profile position, surface defects are considered as part of the specified surface in the default case
