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GB/T 38762 consists of the following parts, under the general title Geometrical product specification (GPS) - Dimensional tolerancing:
——Part 1: Linear sizes;
——Part 2: Dimensions other than linear or angular sizes;
——Part 3: Angular sizes.
This is Part 3 of GB/T 38762.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This standard has been redrafted and modified in relation to ISO 14405-3: 2016 Geometrical product specifications (GPS) - Dimensional tolerancing - Part 3: Angular sizes.
The main technical differences with respect to ISO 14405-3: 2016 are as follows:
——the adjustments on technical differences are made for the normative references of this Part to adapt to the technical conditions in China. The adjustments are mainly reflected in clause 2 "Normative references", which are shown as follows:
ISO 8015 is replaced by GB/T 4249, which is modified in relation to the international standard;
ISO 17450-1 is replaced by GB/T 24637.1, which is modified in relation to the international standard;
ISO 17450-2 is replaced by GB/T 24637.2, which is modified in relation to the international standard;
ISO 17450-3 is replaced by GB/T 24637.3, which is modified in relation to the international standard;
ISO 14405-1: 2016 is replaced by GB/T 38762.1-2020, which is modified in relation to the international standard;
ISO 14405-2 is replaced by GB/T 38762.2, which is modified in relation to the international standard.
The following editorial changes have been made in this part:
——the second paragraph of Clause 3 is changed to as a note;
——the related standards in D.4 are added in Annex D (informative).
This part was proposed by and is under the jurisdiction of National Technical Committee on Geometrical Product Specifications of Standardization Administration of China (SAC/TC 240).
Geometrical product specifications (GPS) - Dimensional tolerancing - Part 3: Angular sizes
1 Scope
This part of GB/T 38762 establishes the default specification operator for angular size and defines a number of special specification operators for features of angular size: cone (truncated, i.e. frustum, or not), wedge (truncated or not), two opposite straight lines (intersection of a wedge/truncated wedge and a plane perpendicular to the intersection straight line of the two planes of the wedge/truncated wedge, intersection of a cone/frustum and a plane containing the axis of revolution of the cone/frustum). See Figure 1 and Figure 2.
This part also defines the specification modifiers and the drawing indications for these angular sizes.
This part covers the following angular sizes:
——local angular size:
a) angular size between two lines;
b) portion angular size;
——global angular size:
a) direct global angular size:
1) least squares angular size;
2) minimax angular size;
b) rank-order angular size/indirect global angular size:
1) maximum angular size;
2) minimum angular size;
3) average angular size;
4) range of angular sizes;
5) mid-range angular size;
6) median angular size;
7) standard deviation of angular size.
This part defines the meaning of tolerances of angular sizes indicated as:
——+ and/or - limit deviations, e.g. 0°/-0.5°;
——indicated with upper limit of size (ULS) and/or lower limit of size (LLS), e.g. 35° max. or 15° min., 34°/36°;
——with or without modifiers.
This part provides a set of tools to express several types of angular size characteristics. It does not give any information on the relationship between a function or a use and an angular size characteristic.
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/T 4249 Geometrical product specifications (GPS) - Fundamentals - Concepts, principles and rules (GB/T 4249-2018, ISO 8015:2011, MOD)
GB/T 24637.1 Geometrical product specifications (GPS) - General concepts - Part 1: Model for geometrical specification and verification (GB/T 24637.1-2020, ISO 17450-1:2011, MOD)
GB/T 24637.2 Geometrical product specifications (GPS) - General concepts - Part 2: Basic tenets, specifications, operators, uncertainties and ambiguities (GB/T 24637.2-2020, ISO 17450-2:2012, MOD)
GB/T 24637.3 Geometrical product specifications (GPS) - General concepts - Part 3: Toleranced features (GB/T 24637.3-2020, ISO 17450-3:2016, MOD)
GB/T 38762.1-2020 Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes (ISO 14405-1:2016, MOD)
GB/T 38762.2 Geometrical product specifications(GPS) - Dimensional tolerancing - Part 2: Dimensions other than linear or angular sizes (GB/T 38762.2-2020, ISO 14405-2:2018, MOD)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 4249, GB/T 24637.1, GB/T 24637.2, GB/T 24637.3, GB/T 38762.1 and GB/T 38762.2 and the following apply.
Note: For association criteria, it is assumed that the terms “least squares” and “Gaussian” are equivalent, as well as “minimax” and “Chebyshev”. In this document, the terms “least squares” and “minimax” are retained. The least squares criterion is understood without material constraint throughout this part.
3.1
angular size
angular dimension of a cone or between two coplanar opposite straight lines or between two opposite non parallel planes
Note 1: The angular size is defined from nominal features or from associated features which are angular features of size.
Note 2: See example of angular size on Figure 1 and Figure 2.
Note 3: Definition of “angular feature of size (feature of angular size)” is given in GB/T 24637.1, the angle dimension cannot be 0° or 180°.
Note 4: Angular features of size are of two types.
——Revolute angular feature of size: a cone or a frustum. Two opposite straight lines are established from a longitudinal section of a cone/frustum with a plane containing the associated axis of revolution of the cone/frustum.
——Prismatic angular feature of size: a wedge (truncated or not). Two opposite straight lines are established from a cross section of a wedge/truncated wedge with a plane perpendicular to the intersection straight line of the two associated planes of the wedge/truncated wedge.
Note 5: Figure 1 and Figure 2 illustrate angular features of size type wedge, cone, frustum and two lines.
Note 6: Figure 3a) and Figure 3b) illustrate the case of an angular feature of size and an angular distance between two planes which is not an angular feature of size and shows that an angular feature of size exists when the material directions are opposed (when one of the features is rotated around their intersection line to coincide with the other feature, then the material is on the opposite sides for the two features). See also Annex B.
Note 7: Envelope requirement cannot be applied for angular features of size.
a) Wedge b) Cone
c) Truncated wedge d) Frustum
Figure 1 Examples of areal angular features of size
a) Two opposite lines of a wedge b) Two opposite generatrix lines of a cone
Figure 2 Examples of angular features of size
a) Example # 1 b) Example # 2
Keys:
1——feature of angular size;
2——non-feature of angular size.
Figure 3 Examples of possible angular features of size
3.2
local angular size
local angular size characteristic
angular size characteristic having a unique value for a specific location and a non-unique value along and/or around the angular feature of size
Note 1: For a given feature, an infinite number of local angular sizes exists.
Note 2: In Figure 4, an example of local angular size is shown.
Note 3: Two local angular size associations can be specified: least squares local angular size and minimax local angular size. See Annex A.
Keys:
1——real angular feature of size;
2——associated planes with (1);
3——intersection straight line of (2);
4——perpendicular cross section to (3);
5——two extracted lines;
6——two associated straight lines;
7——two-line angular size.
Figure 4 Two-line angular size
3.2.1
two-line angular size
local angular size between two lines
angle between two associated straight lines established from two extracted lines obtained from the intersection with an intersection plane defined from the associated angular feature of size
Note 1: See Figure 4.
Note 2: The process for establishing the two-line angular size depends on the invariance class of the feature: revolute surface or prismatic surface.
Note 3: The default specification operator defining the two-line angular size is described in Annex A.
3.2.1.1
two-line revolute angular size
two-line angular size (3.2.1) where the straight lines are associated with two extracted lines resulting from the intersection of an extracted revolute feature with a plane containing its associated axis
Note: The axis of the associated revolute feature is the “directly associated median line” described in GB/T 38760-2020, 3.5.1.2.4.
3.2.1.2
two-line prismatic angular size
two-line angular size (3.2.1) where the straight lines are associated with two extracted lines resulting from the intersection of two extracted surfaces with a plane perpendicular to their associated straight line of intersection
3.2.2
portion angular size
global angular size (3.3) for a given portion of the extracted angular feature of size
Note 1: A portion angular size is a local angular size when taking into account the complete angular feature of size and a global angular size when taking into account only the specific portion.
Note 2: See Figure 5.
Note 3: A portion angular size can be a direct global angular size (3.3.1) or an indirect global angular size (3.3.2).
Note 4: The operator for defining a portion is not covered by this part.
Foreword i
1 Scope
2 Normative References
3 Terms and Definitions
4 Specification modifiers and symbols
5 Default specification operator for angular size
6 Drawing indication
Annex A (Normative) Association criteria for two-line angular size (for a revolute or prismatic feature of size)
Annex B (Informative) Differences between two planes considered as an angular feature of size and two planes considered as two single features
Annex C (Informative) Overview diagram for angular size
Annex D (Informative) Relation to GPS matrix
Bibliography
