ISO 1101 Rule Set
Geometrical product specification (GPS) is a symbolic language for communicating design requirements in models and on technical drawings. However, GPS involves over 100 standards, many of which do not have a direct impact on application of GD&T to the design model. ISO 14638 provides the overview of the international standardization of GPS, explains the concept of GPS and provides a master plan of GPS including the existing and future standards. The basis for GPS is geometric dimensioning and tolerancing (GD&T) as specified in ISO 1101.
The GD&T Advisor ISO 1101 rule set is based on the following standards:
• ISO 1101 – Geometric Product Specifications (GPS) – Geometrical tolerancing – Tolerances of form, orientation, location, and run-out — Contains basic information and gives requirements for the geometrical tolerancing of workpieces. It represents the initial basis and defines the fundamentals for geometrical tolerancing. (See Note 1)
• ISO 16792 – Technical product documentation – Digital product definition practices – Defines the rules for displaying of annotations on the design model (see Note 2)
• ISO 8015 – Geometrical product specifications (GPS) – Fundamentals – Concepts, principles and rules — Specifies the principle of the relationship between dimensional (linear and angular) tolerances and geometrical tolerances.
• ISO 2768-1 – General tolerances – Tolerances for linear and angular dimensions without individual tolerance indications — Specifies general tolerances for linear and angular dimensions without indications.
• ISO 2768-2 – General tolerances – Geometrical tolerances for features without individual indications — Specifies general geometrical tolerances to control those features which have no respective individual indications. (See Note 3)
• ISO 5459 – Geometrical product specifications (GPS) – Geometrical tolerancing – Datums and datum systems — Describes datum and datum systems for geometrical tolerancing, their definitions, practical embodiments, and their indications.
• ISO 5458 – Geometrical Product Specification (GPS) – Geometrical tolerancing – Positional tolerancing
• ISO 2692 – Geometrical Product Specification (GPS) – Geometrical tolerancing – Maximum material requirement (MMR), least material requirement (LMR), and reciprocity requirement (RPR)
• ISO 286 – Geometrical product specifications (GPS) – ISO code system for tolerances on linear sizes
• ISO 10579 – Geometrical product specifications (GPS) – Dimensioning and tolerancing – Non-rigid parts
• Other related standards
These standards have requirements that the design model include notes indicating the applicable standards. See Standard Reference Notes for more information.
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1. Clause 2 of ISO 1101 provides a list of referenced standards and states:
The following referenced documents are indispensable for this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
For the most part, the standards listed above are dated references in ISO 1101, so only the edition cited (rather than the latest edition) applies. For more information on this topic, refer to The ISO Geometrical Product Specification Handbook, by Henrik S. Nielsen. This book is highly recommended for anyone using GD&T Advisor for parts based on ISO GPS.
2. ISO 16792 specifies the requirements for models and the exceptions or additional requirements for views on technical drawings. GD&T Advisor creates annotations according to the model requirements.
3. The reference to ISO 2768 includes a letter (H, K, or L) representing the class of general geometrical tolerances. According to ISO 2768-2, the general geometrical tolerance applies to features that do not otherwise have a geometrical tolerance indication and may be used to constrain straightness, flatness, parallelism, perpendicularity, symmetry, or circular run-out. General geometrical tolerances are not applicable to other geometric characteristics.
There may be problems in the interpretation of general geometrical tolerances that may constrain the location or orientation of the feature. Generally speaking, geometrical tolerances that constrain location or orientation of the feature require a reference to a datum reference frame (DRF). However, there is no DRF referenced by general geometrical tolerances, so the meaning of general geometrical tolerances for parallelism, perpendicularity, symmetry, and circular run-out may be ambiguous. Furthermore, ISO 2768-2 states that 'workpieces exceeding the general geometrical tolerance shall not lead to automatic rejection, provided that the function is not impaired'. Thus, use of general geometrical tolerances for defining the permissible deviation of the location or the orientation of the feature is not recommended. For these reasons, GD&T Advisor considers general geometrical tolerances of form (e.g., straightness and flatness) but no other geometrical tolerances (e.g., parallelism, perpendicularity, symmetry, or circular run-out).
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