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GB/T 40742.3-2021 English PDF (GBT40742.3-2021)

GB/T 40742.3-2021 English PDF (GBT40742.3-2021)

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GB/T 40742.3-2021: Geometrical product specifications (GPS). Geometrical precision verification -- Part 3: Functional gauges and fixtures. Verification when applying maximum material requirements and minimum material requirements
This document specifies the general rules for inspection and verification process when applying maximum material requirements and least material requirements and the general requirements for the design of test fixtures. This document applies to the inspection and verification of measured features and/or datum features when the maximum material requirements and least material requirements are applied using functional gauges and fixtures.
GB/T 40742.3-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 17.040.40
CCS J 42
Geometrical product specifications (GPS) - Geometrical
precision verification - Part 3: Functional gauges and
fixtures - Verification when applying maximum material
requirements and minimum material requirements
ISSUED ON: OCTOBER 11, 2021
IMPLEMENTED ON: MAY 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
Introduction ... 4
1 Scope ... 6
2 Normative references ... 6
3 Terms and definitions ... 7
4 General provisions ... 9
5 Fixture ... 13
Appendix A (Informative) Material functional gauge ... 14
Appendix B (Informative) Relationship to GPS matrix model ... 17
References ... 19
Geometrical product specifications (GPS) - Geometrical
precision verification - Part 3: Functional gauges and
fixtures - Verification when applying maximum material
requirements and minimum material requirements
1 Scope
This document specifies the general rules for inspection and verification process when applying maximum material requirements and least material requirements and the general requirements for the design of test fixtures.
This document applies to the inspection and verification of measured features and/or datum features when the maximum material requirements and least material requirements are applied using functional gauges and fixtures.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the version corresponding to that date is applicable to this document; for undated references, the latest version (including all amendments) is applicable to this document. GB/T 1182, Geometrical product specifications (GPS) - Geometrical tolerancing - Tolerances of form, orientation, location and run-out
GB/T 8069, Functional gauges
GB/T 16671, Geometrical product specifications (GPS) - Geometrical tolerancing - Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR)
GB/T 17851, Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum systems
GB/T 24637.1, Geometrical product specifications (GPS) - General concepts - Part 1: Model for geometrical specification and verification
GB/T 24637.2, Geometrical product specifications (GPS) - General concepts - Part 2: Basic tenets, specifications, operators, uncertainties and ambiguities GB/T 38762.1, Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes
3 Terms and definitions
Terms and definitions determined by GB/T 1182, GB/T 8069, GB/T 16671, GB/T 17851, GB/T 24637.1, GB/T 24637.2 and GB/T 38762.1, as well as the following, are applicable to this document.
3.1
feature of size
Geometric feature with one or more substantive characteristics, only one of which can be used as a variable parameter, and the rest are part of the “single parameter family” and obey the single constraint attribute of this parameter.
[Source: GB/T 16671-2018, 3.2, modified]
3.2
local size
Along and/or around the direction of the feature of size, the size characteristics of the feature of size may have non-unique evaluation results.
Note 1: For a given element, there are multiple local sizes.
Note 2: The two-point size of two opposite planes can be called “two-point thickness” or “two-point width”.
[Source: GB/T 38762.1-2020, 3.6]
3.3
external function size
Direct global size of the associated integral feature obtained from the extracted integral feature using a fitting criterion with material external constraints. The associated integral feature is of the same form type as the feature of size (see 3.1) and is in external contact with the extracted integral feature.
Note 1: See 3.7.1 of GB/T 38762.1-2020 for the definition of direct global size. Note 2: When performing the fitting operation on the extracted integral feature, the available fitting criteria include least squares, maximum inscribed, minimum circumscribed and minimax criteria, and the direct global size respectively include the least-squares size (see GB/T 38762.1-2020, 3.7.1.1), maximum functional gauge
A full-scale general gauge that is used – when the maximum material requirement or the least material requirement is applied to the measured features and/or datum features – to determine whether their actual contours exceed the boundary (maximum material virtual boundary, maximum material boundary, least material virtual boundary or least material boundary).
Note 1: Functional gauge can be divided into material functional gauge and virtual functional gauge according to the state of space existence. Material functional gauge is a physical functional gauge, and the virtual functional gauge is a digital functional gauge.
Note 2: Material functional gauges are mainly used in occasions where the maximum material requirement is applied to verify the measured features and (or) datum features. Material functional gauges can have four structural types: integral type, combination type, insertion type and active type (See 3.1 of GB/T 8069). See Appendix A for examples of various types of material functional gauges. Note 3: The virtual functional gauge is a digital gauge designed according to the functional requirements and structural shape characteristics of the workpiece to be tested. It is virtually a method of digitally processing measurement data, which can be used in occasions where the maximum material requirement or least material requirement is applied to verify the measured features and (or) datum features.
[Source: GB/T 8069-1998, 3.1, modified]
3.8
fixture
A device used – during the testing process – to fix parts so that they have a specified position for testing.
4 General provisions
4.1 General
The maximum material requirement and the least material requirement, which can be used for the measured features and datum features belonging to the feature of size, specify the comprehensive requirements between the size of the feature of size and the geometric characteristics (form, orientation or position) of the derived features. For the detection and verification of feature of size when applying the maximum material requirement or the least material requirement, functional gauges can be used to check whether the actual contours of the measured features and (or) the datum features exceed their maximum material virtual boundary, maximum material boundary, lease material virtual condition or least material boundary.
4.2 Test when applying the maximum material requirement
4.2.1 Test when applying the maximum material requirement to the measured feature
4.2.1.1 When the maximum material requirement is applied to the measured feature, first check the eligibility of the local size of the measured feature, then use the functional gauge to check whether the actual contour of the measured feature exceeds the maximum material virtual boundary. Qualified local size shall be within its allowable limit range of sizes.
Note 1: When the material functional gauge is used for inspection, the inspection part of the material functional gauge is a full-scale general gauge. The size, shape, direction and position of the inspection part of the material functional gauge shall be the same as the size, shape, direction and position of the boundary of the measured feature (maximum material virtual boundary or maximum
material boundary). See GB/T 8069 for the dimensional tolerance, form and position tolerance and allowable wear of material functional gauges. Refer to Appendix A for design principles of material functional gauges.
Note 2: When the virtual functional gauge is used to test the measured feature of external size, the criteria for the qualified measured feature are:
1) The external function size (see 3.3) of the measured feature is equal to or smaller than the maximum material virtual size (MMVS);
2) The local size (see 3.2) of any position of the measured feature is equal to or smaller than the maximum material size (MMS) and equal to or larger
than the least material size (LMS).
Note 3: When the virtual functional gauge is used to inspect the measured feature of internal size, the criteria for the qualified measured feature are:
1) The internal function size (see 3.4) of the measured feature is equal to or greater maximum material virtual size (MMVS);
2) The local size (see 3.2) of any position of the measured feature shall be equal to or greater than the maximum material size (MMS) and equal to or less than the least material size (LMS).
4.2.1.2 When the measured feature adopts the reversible maximum material requirement, use the functional gauge to check whether the actual contour of the measured feature exceeds the maximum material virtual boundary.
2) The local size (see 3.2) of any position of the measured feature is equal to or smaller than the maximum material size (MMS) and equal to or larger
than the least material size (LMS).
Note 3: When the virtual functional gauge is used to inspect the measured feature of internal size, the criteria for the qualified measured feature are:
1) The internal function size (see 3.4) of the measured feature is equal to or less than the least material virtual size (LMVS);
2) The local size (see 3.2) of any position of the measured feature shall be equal to or greater than the maximum material size (MMS) and equal to or less than the least material size (LMS).
4.3.1.2 When the measured feature adopts the reversible least material requirement, use the virtual functional gauge to check whether the actual contour of the measured feature exceeds the least material virtual boundary.
4.3.1.3 When the zero form and position tolerance of the least material requirement is applied to the measured feature, use the virtual functional gauge to check whether the actual contour of the measured feature exceeds the least material boundary. 4.3.2 Test when applying the least material requirement to the datum feature 4.3.2.1 When the datum feature is not given with the geometric specification, or is given with the geometric specification, but there is no symbol ○L after the geometric tolerance value, it is necessary to check whether the local size of the datum feature is qualified, and check whether the actual contour of the datum feature is beyond its least material boundary at the same time.
4.3.2.2 When the datum feature is given with the geometric specification, and there is a symbol ○L after the geometric tolerance value, it is necessary to check whether the local size of the datum feature is qualified, and check whether the actual contour of the datum feature is beyond its least material virtual boundary at the same time. 4.4 Inspection rules
When inspecting workpieces, the operator shall use new-made or less-worn material functional gauges.
Note 1: In general, the inspector shall use the same type of material functional gauge used by the operator; the user representative shall use the functional gauge of the same type used by the operator but close to the maximum material virtual boundary (MMVB).
Note 2: When objection arises when using the material functional gauge to inspect the workpiece, a material functional gauge close to the maximum material virtual boundary (MMVB) shall be used for arbitration.
4.5 Inspection conditions
Unless other inspection conditions are specified, ideal inspection conditions shall be: -- standard temperature 20 °C;
-- standard measuring force 0 N;
-- relative humidity: Excessive humidity will lead to corrosion of the metal surface and deterioration of the measuring component, and also cause discomfort to the measuring personnel, both of which may have a negative impact on the
measurement accuracy, therefore, it is recommended that the relative humidity should not exceed 45%;
-- Contamination: Contamination of the measurement environment will have an adverse effect on the accuracy of the measuring tool, therefore, when measuring, ensure that there is no influence of grease, dirt, etc., and maintain a clean measurement environment;
-- Other appearance defects such as surface scratches, abrasions and turned-down edges of the measured feature shall be excluded;
-- The measuring surface of the gauge shall not have rust, burrs, black spots, scratches and other defects that obviously affect the quality of appearance and use, and other surfaces shall not have rust and cracks.
5 Fixture
Fixtures usually consist of positioning devices, clamping devices, transfer devices, motion guides and other auxiliary components.
Generally, fixtures and gauges share the same datum features. When designing fixtures, the impact on the measurement accuracy from the form and direction of the fixture components in contact with datum features of the part and the form error of the fixture positioning datum surface shall be considered.
If the datum feature is an outline feature, the size, shape, direction and position of the positioning part shall be the same as the ideal feature of the actual datum feature. A.2.4 Guiding part
The part on the material functional gauge that is convenient for the inspection part and (or) the positioning part to enter the measured feature and (or) the datum feature. The shape, direction and position of the guiding part shall be the same as the shape, direction and position of the inspection part or positioning part.
When the inspection part or the positioning part is also used as the guiding part (no step type), the size of the guiding part shall be determined by the inspection part or the positioning part.
The size of the stepped guiding part shall be determined by the designer, but shall be standardized.
A.3 Establishment of the datum of material functional gauge
When the maximum material requirement is applied to the datum feature of the workpiece, the datum of the material functional gauge shall be established according to the positioning part determined by the boundary (maximum material boundary or maximum material virtual boundary) of the datum feature.
When the maximum material requirement is not applied to the datum feature of the workpiece, the datum shall be established according to the positioning part determined by the actual datum feature.
A.4 Inspection methods
Material functional gauges can be used in two ways: sequential inspection and common inspection. Sequential inspection is mainly used for process inspection, and common inspection is mainly used for final inspection.
Sequential inspection is a way of using different material functional gauges to sequentially inspect the form and position error and (or) size of the datum feature and the orientation or positioning error of the measured feature.
Common inspection is a way of using the same material functional gauge to inspect the orientation or positioning error of the measured feature and the form and position error and (or) size of the datum feature.
A.5 Technical requirements for material functional gauge
The technical requirements for material functional gauge are as follows: a) When the working part of the material functional gauge is a feature of size, the dimensional tolerance shall adopt the envelope requirements;
b) The orientation or location tolerance of the working part of the material functional gauge shall generally follow the principle of independence. If necessary and possible, the orientation or location tolerance of the working part of the master gauge can adopt the maximum material requirement;
c) The undeclared tolerance of the linear size of the material functional gauge is generally level m, and the undeclared form and location tolerance is generally level H;
d) There shall be no rust, burrs, black spots, scratches, cracks and other defects that obviously affect the appearance and quality of use on each working surface of the material functional gauge, and there shall be no rust and cracks on the non- working surface;
e) The assembly of each part of the material functional gauge shall be correct, the connection shall be firm and reliable, and no loosening shall occur during use; f) The material of material functional gauge shall be provided with long-term dimensional stability;
g) The hardness of the working surface of steel material functional gauge shall not be lower than 700 HV (60 HRC);
h) Material functional gauges shall be subjected to stability treatment; i) The surface roughness Ra value of the working surface of material functional gauge shall not be greater than 0.2 μm, and the Ra value of the non-working surface shall not be greater than 3.2 μm. (Except for surfaces obtained with non- removable material.)
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