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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 1 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 14405-1: 2016 Geometrical product specifications (GPS) - Dimensional tolerancing - Part 1: Linear sizes.
The main technical differences with respect to ISO 14405-1: 2016 are as follows:
——the adjustment on technical differences are made for the 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 286-1 is replaced by GB/T 1800.1, which is modified in relation to the international standard;
? ISO 8015 is replaced by GB/T 4249, which is modified in relation to the international standard;
? ISO 81714-1 is replaced by GB/T 16901.1, 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: 2012 is replaced by GB/T 24637.2-2020, which is modified in relation to the international standard;
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? ISO 17450-3 is replaced by GB/T 24637.3, which is modified in relation to the international standard;
This part was proposed by and is under the jurisdiction of SAC/TC 240 National Technical Committee on Geometrical Product Specifications of Standardization Administration of China.
Geometrical product specifications (GPS) - Dimensional tolerancing -
Part 1: Linear sizes
1 Scope
This part of GB/T 38762 establishes the default specification operator (see GB/T 24637.2) for linear size and defines a number of special specification operators for linear size for features of size, e.g. “cylinder”, “sphere”, “torus,”1), “two parallel opposite planes”, or “two parallel opposite straight lines”. It also defines the specification modifiers and the drawing indications for these linear sizes.
This part covers the following linear sizes:
a) local size:
——two-point size;
——spherical size;
——section size;
——portion size.
b) global size:
——direct global linear size;
——least-squares size;
——maximum inscribed size;
——minimum circumscribed size;
——minimax size;
——indirect global linear size.
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c) calculated size:
——circumference diameter;
——area diameter;
——volume diameter.
d) rank-order size:
——maximum size;
——minimum size;
——average size;
——median size;
——mid-range size;
——range of sizes;
——standard deviation of sizes.
This part defines tolerances of linear sizes with or without modifiers (see Tables 1 and 2) for the following:
——+/- limit deviation (e.g. 0/-0.019) (see Figure 11);
——an upper limit of size (ULS)/lower limit of size (LLS) (e.g. 15.2 max., 12 min., or 30.2/30.181) (see Figure 13);
——an ISO tolerance class code in accordance with GB/T 1800.1 (e.g. 10 h6) (see Figure 12).
This part provides a set of tools to express several types of size characteristic. It does not present any information on the relationship between a function and a size characteristic.
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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 1800.1 Geometrical product specifications (GPS) - ISO code system for tolerances on linear sizes - Part 1:Basis of tolerances, deviations and fits (GB/T 1800.1-2020; ISO 286-1: 2010, MOD)
GB/T 4249 Geometrical product specifications (GPS) – Fundamentals - Concepts, principles and rules (GB/T 4249-2018; ISO 8015: 2011, MOD)
GB/T 16901.1 Rules for the presentation of graphical symbols for use in technical product documentation－Part 1: Basic rules (GB/T 16901.1-2008; ISO 81714-1: 1999, 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 24637.2-2020 Geometrical product specifications (GPS) - General concepts - Part 2: Basic tenets, specifications, operators, uncertainties and ambiguities (ISO 17450-2: 2012, MOD)
GB/T 24637.3 Geometrical product specifications (GPS) - General concepts - Part 3: Toleranced features (GB/T 2463 7.3-2020; ISO 17450-3: 2016, MOD)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB/T 1800.1, GB/T 4249, GB/T 24637.1, GB/T 24637.2 and GB/T 24637.3 as well as the following apply.
3.1
feature of size
feature of linear size or feature of angular size
Notes:
1 Feature of linear size and feature of angular size are synonyms of linear feature of size and angular feature of size, respectively
2 Figures 1 and 2 illustrate a linear feature of size, type cylinder, or two parallel opposite planes.
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3 This part only deals with features of linear size which can be a cylinder, a sphere, two parallel opposite planes, a circle (intersection of a revolute surface and a plane perpendicular to the axis of the associated surface), two parallel opposite straight lines (the intersection of a cylindrical surface and a plane containing the associated axis of the cylindrical surface or a prismatic surface and a plane perpendicular to the associated median plane of the prismatic surface), and two opposite circles (the intersection of a pair of coaxial revolute surfaces and a plane perpendicular to the axis of one of the revolute surfaces), i.e. the wall thickness of a tube.
4 Two parallel opposite straight lines can be symmetrically established from the associated axis for a cylindrical surface or a plane perpendicular to the plane of a prismatic surface. Two opposite circles can be established from the intersection of a pair of coaxial revolute surface and a plane perpendicular to the axis of one the revolute surfaces or intersection of a collection of two single surfaces and a section feature which is a cylinder.
a) Nominal features of size (internal and external)
b) Extracted feature
Key:
a——size of internal linear feature of size;
b——size of external linear feature of size.
Figure 1 Example of a linear feature of size consisting of two opposite planes
a) Nominal features of linear size (internal and external)
b) Extracted feature
Key:
a——size of internal linear feature of size;
b——size of external linear feature of size.
Figure 2 Example of a linear feature of size consisting of a cylinder
3.2
upper limit of size; ULS
upper limit of size characteristic
largest permissible value for a size characteristic (3.5)
3.3
lower limit of size; LLS
lower limit of size characteristic
smallest permissible value for a size characteristic (3.5)
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3.4
size
dimensional parameter considered variable for a feature of size (3.1) that can be defined on a nominal feature or on an associated feature
Notes:
1 In this part, the size is linear, e.g. the diameter of a cylinder or the distance between two parallel opposite planes, two opposing lines, and two concentric circles. Depending on the type of linear feature of size, the terms “diameter”, “width”, and “thickness” are synonyms for size.
2 A size is angular (e.g. angle of a cone) or linear (e.g. diameter of a cylinder). This part only deals with linear size.
3.5
size characteristic
characteristic relative to a size (3.4) and defined from an extracted integral feature
Notes:
1 See Annex B, Figure B.1.
2 A size can be evaluated by more than one size characteristic (e.g. the two-point diameter or the diameter of the associated feature taken on the extracted feature).
3.6
local size
local linear size
local size characteristic
local linear size characteristic
size characteristic (3.5) having by definition a non-unique result of evaluation along and/or around a feature of size
Foreword i
1 Scope
2 Normative references
3 Terms and definitions
4 Specification modifiers and symbols
5 Default specification operator for size
6 Drawing indication for special specification operators for size
7 Indication of the toleranced feature on which the size characteristic is defined
8 Complementary indication
Annex A (Normative) Proportions and dimensions of symbols
Annex B (Informative) Overview diagram for sizes
Annex C (Informative) Data handling with rank-order modifiers
Annex D (Normative) Size characteristics
Annex E (Normative) Drawing rules for location and indication of the size specification
Annex F (Informative) Relation to the GPS matrix model
Bibliography
