This standard is identical with International Standard ISO 5458:1998 Geometrical Product Specifications (GPS) — Geometrical Tolerancing — Positional Tolerancing (English version).
This standard replaces GB/T 13319-1991 Geometrical Tolerance — Positional Tolerancing in whole.
This standard is equivalent to a translated version of ISO 5458:1998.
For the purposes of this standard, the following editorial changes have also been made:
a) Since GB/T 18780.1 (which is identical with ISO 14660-1) has been formulated in China and put into the Normative References, the Annex A (Informative) Definition of ISO 5458 (as given in ISO 14660-1) is deleted.
b) "This International Standard" is changed to "this standard";
c) Foreword and introduction of ISO 5458 are deleted;
The following technical deviations have been made with respect to the GB/T 13319-1991 (the previous edition):
— Major changes have been made in the content and layout of the standard, and the standard name is revised.
— Reference codes in the diagram are changed to the reference codes equivalent to the ISO standard.
— The content not found in ISO 5458 is deleted.
Annexes A, B and C of this standard are for information only.
This standard was proposed by and is under the jurisdiction of National Technical Committee 240 on Product Dimension and Geometric Element Specifications of Standardization Administration of China.
The previous editions of this standard are as follows:
— GB/T 13319-1991.
Geometrical Product Specifications (GPS) — Geometrical Tolerancing — Positional Tolerancing
1 Scope
This standard specifices the positional tolerancing.
The positional tolerancing of this standard is applicable to the location of a point, of a line nominally straight and of a surface nominally plane, e.g. the centre of a sphere, the axis of a hole or shaft and the median surface of a slot.
Note: Profile tolerancing is used when lines are not intended to be straight or surfaces are not intended to lie in a plane.
2 Normative References
The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections), or revisions, of any of these publications do not apply to this part. However parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
GB/T 18780.1-2002 Geometrical Product Specifications (GPS) — Geometrical Features — Part 1: General Terms and Definitions (ISO 14660-1, IDT)
ISO 1101 Geometrical Product Specifications (GPS) — Geometrical Tolerancing — Generalities, Definitions, Symbols, Indication on Drawings
3 Terms and Definitions
For the purpose of this standard, the term and definitions related to positional tolerancing and given in ISO 1101, and the term and definitions related to features and given in GB/T 18780.1 apply.
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4 Establishment of Positional Tolerances
4.1 General
The primary constituents are theoretically exact dimensions, tolerance zones and datums.
4.2 Fundamental requirements
Positional tolerances are associated with theoretically exact dimensions and define the limits for the location of actual (extracted) features, such as points, axes, median surfaces, nominally straight lines and nominally plane surfaces relative to each other or in relation to one or more datums.
The tolerance zone is symmetrically disposed about the theoretically exact location.
Note: Positional tolerances do not accumulate when theoretically exact dimensions are arranged in a chain (see Figure 4). (This contrasts with dimensional tolerances that are arranged in a chain.) Positional tolerancing allows clear reference to be made to one or more datums.
4.3 Theoretically exact dimensions
In the indication of positional tolerance, the heoretically exact dimensions are the dimensions used to determine the ideal position of each feature, such dimensions are not directly accompanied by tolerances.
Theoretically exact dimensions, both angular and linear, are indicated by being enclosed in a rectangular frame in accordance with GB/T 1182. This is illustrated in Figures 2 a), 2 b), 3 a), 4 a), 5 a) and 7 a).
The theoretically exact dimensions 0° and 90°, 180° or distance 0 [see Figure 1 a), Figure 2 a), Figure 4 a) and Figure 5 a)], are implied without specific indication.
When the positional tolerance features share the same centreline or axis they are regarded as theoretically exactly related features, unless otherwise specified, e.g. in relation to different datums or other reason indicated by an appropriate note on the drawing as shown in Figure 2 b).
a) Indication b) Explanation
Figure 1
Annex A gives an example for indication of the theoretically exact dimensions.
4.4 Positional tolerances on a complete circle
When positionally toleranced features are arranged in a complete circle it is understood that the features are equally spaced, unless otherwise stated, and that their locations are theoretically exact.
If two or more groups of features are shown on the same axis, they shall be considered to be a single pattern when they are not related to a datum or they are related to the same datum or datum system (datums in the same order of precedence or under the same material conditions) [see Figure 2 a)]; unless otherwise stated [see Figure 2 b)].
Foreword II
1 Scope
2 Normative References
3 Terms and Definitions
4 Establishment of Positional Tolerances
5 Tolerance Combinations
Annex A (Informative) Positional Tolerancing Instead of Dimensional Tolerancing
Annex B (Informative) Relation to the GPS Matrix Model
Annex C (Informative) Bibliography
