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GB/T 4249-2018 English PDF (GBT4249-2018)

GB/T 4249-2018 English PDF (GBT4249-2018)

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GB/T 4249-2018: Geometrical product specifications (GPS) -- Fundamentals -- Concepts, principles and rules

This Standard specifies the fundamental concepts, principles and rules that are valid for the creation, interpretation and application of all relevant standards, technical specifications and technical documents to product dimensions, geometrical product specifications (GPS) and inspections. This Standard is applicable to the interpretation for GPS marks on all types of drawings. Drawing referred in this Standard is a broad concept. It includes all documents that express workpiece specifications.
GB/T 4249-2018
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 01.100.20
J 04
Replacing GB/T 4249-2009
Geometrical product specifications (GPS) -
Fundamentals - Concepts, principles and rules
(ISO 8015:2011, MOD)
ISSUED ON: SEPTEMBER 17, 2018
IMPLEMENTED ON: APRIL 01, 2019
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Terms and definitions ... 5
4 Basic assumptions for reading specification on drawing ... 6
5 Basic principles ... 7
6 Marking rules for default specification operator ... 12
7 Marking rules for specific specification operator ... 14
8 Rules described in brackets ... 16
Annex A (informative) Positions in GPS matrix model ... 17
Bibliography ... 19
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009. This Standard replaces GB/T 4249-2009 ?€?Geometrical product specifications (GPS) - Tolerancing principle?€?. Compared with GB/T 4249-2009, the main
technical changes in this Standard are as follows:
-- deleted, added some terms and definitions (see Clause 3 of this Edition, Clause 3 of Edition 2009);
-- moved the content of ?€?Independent principle?€? to the clause of
?€?Fundamental principle?€? (see 5.5 of this Edition, Clause 4 of Edition 2009); -- deleted tolerance (see Clause 5 of Edition 2009);
-- deleted relevant requirements (Clause 6 of Edition 2009);
-- deleted drawing marks of tolerance principle (Clause 7 of Edition 2009); -- added basic assumptions for reading specification on drawing (see Clause 4 of this Edition);
-- added basic principle (see Clause 5 of this Edition);
-- added marking rules for default specification operator (see Clause 6 of this Edition);
-- added marking rules for specific default specification operator (see Clause 7 of this Edition);
-- added rules for expression in brackets (see Clause 8 of this Edition). This Standard uses redrafting method to modify and adopt ISO 8015:2011
?€?Geometrical product specifications (GPS) -- Fundamentals -- Concepts,
principles and rules?€?.
Compared with ISO 8015:2011, there are technical differences in this Standard. The terms involved in these differences have been marked by a vertical single line (-) at the margin of the outer margin. The corresponding technical differences and reasons are as follows:
-- for normative references, this Standard made adjustment for specific technical differences, so as to adapt to the technical conditions of China. See Clause 2 ?€?Normative references?€? for the adjustment. The specific
adjustments are as follows:
?€? used GB/Z 24637.1 that identically adopts International standard to
Geometrical product specifications (GPS) -
Fundamentals - Concepts, principles and rules
1 Scope
This Standard specifies the fundamental concepts, principles and rules that are valid for the creation, interpretation and application of all relevant standards, technical specifications and technical documents to product dimensions, geometrical product specifications (GPS) and inspections.
This Standard is applicable to the interpretation for GPS marks on all types of drawings.
?€?Drawing?€? referred in this Standard is a broad concept. It includes all documents that express workpiece specifications.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/Z 24637.1, Geometrical Product Specifications (GPS) - General
concepts - Part 1: Model for geometrical specification and verification (GB/Z 24637.1-2009, ISO/TS 17450-1:2005, IDT)
GB/Z 24637.2, Geometrical Product Specifications (GPS) - General
concepts - Part 2: Basic tenets, specifications, operators and uncertainties (GB/Z 24637.2-2009, ISO/TS 17450-2:2002, IDT)
ISO/IEC Guide 98-3:2008, Uncertainty of measurement - Guide to the
expression of uncertainty in measurement (GUM:1995)
ISO/IEC Guide 99:2007, International vocabulary of metrology - Basic and general concepts and associated terms (VIM)
3 Terms and definitions
For the purposes of this document, the terms and definitions defined in GB/Z 24637.1, GB/Z 24637.2, ISO/IEC Guide 98-3:2008, ISO/IEC Guide 99:2007 as It is assumed that the interpretation for the tolerance limit is completely same with the interpretation for the functional limit.
4.4 Functional level of workpiece
It is assumed that the workpiece 100% meets the function within the tolerance limit; does not meet the function outside the tolerance limit.
5 Basic principles
5.1 Principle for adoption
Once it adopts one part of ISO GPS system in mechanical engineering product documents, it is equivalent to adopting the entire ISO GPS system, unless otherwise stated in the document, for example, ?€?refer to other related
documents?€?.
?€?Unless otherwise stated in the document?€? means that if the regional, national or enterprise standards referred are marked in the document, it shall use those standards. Do not adopt ISO GPS system to interpret the normative elements specified in the standard.
If it is unnecessary to adopt ISO GPS system, ?€?noting method is according to GB/T 4249?€? may selectively mark within the title bar or near the title bar. NOTE 1: The most common way to adopt ISO GPS system is to use one or more GPS specifications in drawing.
NOTE 2: ISO GPS system is an International standard issued by ISO/TC 213, see GB/T 20308.
NOTE 3: ?€?Adopting the entire ISO GPS system?€? means that unless otherwise specified, if GPS fundamental standard and GPS comprehensive standard are adopted, then the reference temperature specified in GB/T 19765-2005 and the rules for determination specified in GB/T 18779.1 shall be adopted. The purpose of ?€?principle for adoption?€? is to provide formal traceability for those GPS standards and rules.
5.2 Principle for hierarchy of GPS standard
ISO GPS system is hierarchical. Its standard variety, according to hierarchy, contains the following types:
- GPS fundamental standard;
- GPS comprehensive standard;
- GPS general standard;
5.4 Key element principle
One workpiece can be considered to be composed by many key elements that are limited by natural boundaries. Under the situation of default, each GPS specification of one key element applies to the entire key element. Each GPS specification that expresses the relationship between many key elements applies to many key elements. Each GPS specification is only applicable to one key element or one relationship between key elements.
If it is necessary to change this default specification, it needs to clearly mark on the drawing.
NOTE 1: The natural boundaries between key elements usually refer to the boundaries that sudden change happens on the surface normal. But it is not always true. If one workpiece is composed of two hemispherical elements that have same diameter and intermediate cylindrical element, in such case, the surface normal of natural boundaries between key elements does not have sudden change.
NOTE 2: Some marks do not apply to the entire key element, for example, partial area of key element is marked with a long thick dotted line or is marked with ACS (any cross section).
NOTE 3: Some marks apply to many key elements, for example, CZ (combined tolerance zone) is marked.
NOTE 4: Unless otherwise specified, GPS general specification is considered as a series of GPS specifications. Each GPS specification is only applicable to one characteristic of key element or relationship between key elements (see 5.12).
5.5 Independence principle
Under the situation of default, GPS specification of each key element or GPS specification of relationship between key elements is independent from other specifications. They shall be met respectively, unless other standards or special marks are specified in the actual product specification (for example, modifier symbol ???M in GB/T 16671, CZ in GB/T 1182 and ???E in ISO 14405-1).
5.6 Decimal point principle
The numerical values after the decimal point of nominal size and tolerance value that are not indicated shall be zero. This principle is applicable to the drawing and GPS standard.
Example 1: ??0.2 is equivalent to ??0.200000...
Example 2: 2:10 is equivalent to 10.000000...
5.7 Default principle
eliminate any ambiguity of the functional description in the specification. A complete specification operator defines every important detail to be measured for the specification. Therefore, it eliminates the ambiguity of the specification. Inspection of operation is an actual application of specification operator. When the method uncertainty is zero, inspect the sequences of operator and
specification operator which shall be in one-to-one correspondence. When the method uncertainty is not zero, there are differences in two operators or the sequence of two specifications.
Although the inspection operator is not marked in the drawing, it shall get close to the specification operator during the inspection process, so as to ensure the method uncertainty within the allowable range.
5.10.2 Description of duality principle
The duality principle points out:
a) the GPS specification operator that is specified by GPS specification is irrelevant to any measuring procedures or measuring instruments;
b) the inspection operator that is to realize GPS specification operator is irrelevant to the GPS specification itself; but the relationship between it and GPS specification operator is mirror correspondence.
GPS specification does not specify which kind of inspection operator is acceptable. Whether the operator is acceptable or not is inspected by
measuring the uncertainty and specification uncertainty.
5.11 Function control principle
The function of each workpiece is described by function operator. It can be simulated by a series of specification operators. These specification operators once again define a series of measuring and relevant tolerances.
When all functional requirements of workpiece have been clearly described and controlled by GPS specification, such specification is complete. In most cases, since some functions are described / controlled imperfectly, the specification might be incomplete. Therefore, the correlation between function and a series of GPS specifications may be superior or inferior.
Any correlation deficiency between any functional requirements and GPS
specification shall cause the uncertainty of function description.
5.12 General specification principle
For each characteristic that has same type and the relationship between each When the actual specification of any geometric characteristic in the drawing is ISO basic GPS specification that is marked according to GB/T 1182, GB/T 131- 2006, GB/T 17851, and when in or near title bar, altered default general GPS specification is not marked, then ISO default specification operator is required by a current ISO standard that defines corresponding default specification operator. When establishing drawing, the ISO standard that specifies
corresponding default specification operator shall be the latest version. If other earlier versions of ISO standard are required to use, it shall be indicated clearly. NOTE: At present, ISO GPS standard does not give default provisions on all specification operations in all specification operators, so some ISO default specification operators are incomplete.
6.3 Altered default GPS specification
One altered default specification operator shall be defined in relevant document. As a part of a complete specification operator, altered default specification operator shall be rigorously, clearly and completely defined.
Altered default specification operator shall be marked in or near title bar of drawing. When non-ISO GPS standard is applied, it shall at least mark the following information:
- indicate ?€?marking method?€? or ?€?marking method is according to GB/T 4249?€?; - symbol ;
- complete identifier of relevant document and other necessary information (such as date of release).
NOTE: AD represents ?€?altered default?€?.
If altered default specification operator in drawing is more than one, a number is needed to add after each symbol.
Some ISO standards provide to adopt altered ISO default mode, for example ?€?Size ISO 14405 ?€?.
symbol only applies to non-ISO GPS standard.
defined in default specification operator.
NOTE 1: The type of the added supplementary information (requirements) shall be defined by specification modifier (see GB/Z 24637.2).
According to ISO basic specification, in the marked specific specification operator, the operator that is not specified by the supplementary provisions shall be still defined by default specification.
NOTE 2: At present, ISO GPS standard does not give default provisions on all specification operations in all specification operators, so some ISO basic specifications are incomplete. The contents specified in 7.2 shall be applied to the marks of the following two specific specification operators:
- testing key elements that are comply with GB/T 1182, GB/T 131-2006, GB/T 17851 respectively;
- unique default specification of drawing.
7.2 Additional supplementary information (requirements) of ISO basic
specification
When necessary, the additional supplementary information (requirements) of ISO basic specification can change the default operation of ISO basic
specification, for example:
a) fitting rule;
b) filter type;
c) transmission band;
d) probe tip;
e) extraction condition.
When these default specifications are changed for specific design needs, ISO basic specification shall use the following modes to modify:
- for GB/T 1182, add information to the second block of the tolerance marking box;
- for GB/T 131-2006, add information in a~e areas of graphic symbol that the surface structure is complete;
- for ISO 14405-1, add modifier to tolerance mark.
See corresponding standards for details.

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