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ISO 5459:2024(en)
ISO - Cover page
Foreword
Introduction
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols
5 Role of datums
6 General concepts
 6.1 General
 6.2 Intrinsic characteristics of surfaces associated with datum features
  6.2.1 General
  6.2.2 Single datum established from a single feature
  6.2.3 Common datum established from two or more single features simultaneously
  6.2.4 Datum systems established in a defined sequence from two or more single features
 6.3 Single datums, common datums and datum systems
  6.3.1 General
  6.3.2 Single datums
  6.3.3 Common datums
  6.3.4 Datum systems
7 Graphical language
 7.1 General
 7.2 Indication of datum features
  7.2.1 Datum feature indicator
  7.2.2 Datum feature identifier
  7.2.3 Datum targets
 7.3 Specification of datums and datum systems
 7.4 Indication and meaning of rules
  7.4.1 General
  7.4.2 Rules
8 Specification operators for datum
 8.1 ISO default specification operator for datum
 8.2 Special specification operator for datum
  8.2.1 General
  8.2.2 Filtration specification elements for datum
  8.2.3 Association specification elements for datum
 8.3 Drawing-default specification operator for datums
Annex A (normative) Association for datums
Annex B (informative) Invariance classes
Annex C (informative) Examples
Annex D (informative) Former practices
Annex E (informative) Examples of a datum system or a common datum established with contacting features
Annex F (normative) Relations and dimensions of graphical symbols
Annex G (normative) Establishment of a datum coordinate system from a datum system
Annex H (informative) Filter symbols and attached nesting index
Annex I (informative) Issue of orientation and location constraints in datum systems
Annex J (normative) Filtration of a datum feature which is nominally a plane
Annex K (informative) Relation to the GPS matrix model
Bibliography
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International

Standard

ISO 5459
Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems
Spécification géométrique des produits (GPS) — Tolérancement géométrique — Références spécifiées et systèmes de références spécifiées
Reference number
ISO 5459:2024(en)
Third edition
2024-10
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ContentsPage

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 213, Dimensional and geometrical product specifications and verification, collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 290, Dimensional and geometrical product specification and verification, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 5459:2011), which has been technically revised.
The main changes are as follows:
update of the Normative references and Bibliography;
addition of definitions 3.20, 3.20.1 and 3.20.2;
in Table 1, update of the symbol of the datum feature indicator;
in Table 1, addition of the symbol of single datum target indicator, moveable datum target indicator, restricted datum feature, indication of a situation feature and datum coordinate system indicator, and addition of a note;
in Table 2, addition of [SV], [SF] and [SFxx], and addition of a note;
in Clause 6, addition of a paragraph before the example in 6.1, update of 6.2.1 and 6.2.2, replacement of the first paragraph in 6.2.3 and 6.2.4, addition of the last paragraph in 6.3.2 and table titles added in 6.3.2 and subsequent tables renumbered;
in Clause 7, addition of a note in 7.1, update of 7.2.1, 7.3, 7.4.2.1 and 7.4.2.2, update of the text and figures in 7.4.2.4 up to Figure 22, update of the first paragraph of 7.4.2.6, update of Figure 39, addition of a new rule 11 in 7.4.2.11 and a new rule 12 in 7.4.2.12;
addition of a new Clause 8;
in Annex A, update of the text between Figures A.1 and A.2, update of the first paragraph in A.2.1 and of Figure A.4, addition of Notes 1 and 2 in A.2.2.3, and update of the row for the plane in Table A.2;
addition of a new Clause D.4;
update of Annex F, addition of new Annexes G to J, update of Annex K giving the relation to the GPS matrix model.
Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

This document is a geometrical product specification (GPS) standard and is to be regarded as a general GPS standard (see ISO 14638). It influences chain links A to C of the chains of standards on datums.
The ISO GPS matrix model given in ISO 14638 gives an overview of the ISO GPS system of which this document is a part. The fundamental rules of ISO GPS given in ISO 8015 apply to this document and the default decision rules given in ISO 14253-1 apply to the specifications made in accordance with this document, unless otherwise indicated.
For more detailed information on the relationship of this document to other standards and the GPS matrix model, see Annex K.
For the definitive presentation (proportions and dimensions) of symbols for geometrical tolerancing, see ISO 7083.
The previous version of this document dealt only with planes, cylinders and spheres being used as datums. There is a need to consider all types of surfaces, which are increasingly used in industry. The definitions of classes of surfaces as given in Annex B are exhaustive and unambiguous.
This document applies new concepts and terms that have not been used in previous ISO GPS standards. These concepts are described in detail in ISO 14638, ISO 17450-1 and ISO 17450-2; therefore, it is recommended to refer to these standards when using this document.
This document provides tools to express location or orientation constraints, or both, for a tolerance zone. It does not provide information about the relationship between datums or datum systems and functional requirements or applications.
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International StandardISO 5459:2024(en)
Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems

1Scope

This document specifies terminology, rules and methodology for the indication and understanding of datums and datum systems in technical product documentation. This document also provides explanations to assist the user in understanding the concepts involved.
This document defines the specification operator (see ISO 17450-2) used to establish a datum or datum system. The verification operator (see ISO 17450-2) can take different forms (physically or mathematically) and is not the subject of this document.
NOTEThe detailed rules for maximum and least material requirements for datums are given in ISO 2692.

2Normative 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 edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 128-2:2022, Technical product documentation (TPD) — General principles of representation — Part 2: Basic conventions for lines
ISO 1101, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form, orientation, location and run-out
ISO 2692, Geometrical product specifications (GPS) — Geometrical tolerancing — Maximum material requirement (MMR), least material requirement (LMR) and reciprocity requirement (RPR)
ISO 4351, Geometrical product specifications (GPS) — Association
ISO 17450-1, Geometrical product specifications (GPS) — General concepts — Part 1: Model for geometrical specification and verification
ISO 17450-2, Geometrical product specifications (GPS) — General concepts — Part 2: Basic tenets, specifications, operators, uncertainties and ambiguities

3Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 1101, ISO 2692, ISO 4351, ISO 17450-1, ISO 17450-2 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
ISO Online browsing platform: available at https://www.iso.org/obp
IEC Electropedia: available at https://www.electropedia.org/
3.1
situation feature
point, straight line, plane or helix from which the location and orientation of features, or both, can be defined
3.2
datum feature
real (non-ideal) integral feature used for establishing a datum
Note 1 to entry: A datum feature can be a complete surface, a portion of a complete surface, or a feature of size.
Note 2 to entry: An illustration showing the relations between datum feature, associated feature and datum is given in Figure 4.
3.3
associated feature
associated feature for establishing a datum
ideal feature which is fitted to the datum feature with a specific association criterion
Note 1 to entry: The type of the associated feature is by default the same as the type of the nominal integral feature used to establish the datum (for an exception, see 7.4.2.5).
Note 2 to entry: The associated feature for establishing a datum simulates the contact between the real surface of the workpiece and other components.
Note 3 to entry: An illustration showing the relations between datum feature, associated feature and datum is given in Figure 4.
3.4
datum
one or more situation features of one or more features associated with one or more real integral features selected to define the location or orientation, or both, of a tolerance zone or an ideal feature representing for instance a virtual condition
Note 1 to entry: A datum is a theoretically exact reference; it is defined by a plane, a straight line or a point, or a combination thereof.
Note 2 to entry: The concept of datums is inherently reliant upon the invariance class concept (see Annexes A and B).
Note 3 to entry: Datums with maximum material condition (MMC) or least material condition (LMC) are not covered in this document (see ISO 2692).
Note 4 to entry: When a datum is established, for example, on a complex surface, the datum consists of a plane, a straight line or a point, or a combination thereof. The modifier [SL], [PL] or [PT], or a combination thereof, can be attached to the datum identifier to limit the situation feature(s) taken into account relative to the surface.
Note 5 to entry: An illustration showing the relation between datum feature, associated feature and datum is given in Figure 4.
3.5
primary datum
datum that is not influenced by constraints from other datums
3.6
secondary datum
datum, in a datum system, that is influenced by an orientation constraint from the primary datum in the datum system
3.7
tertiary datum
datum, in a datum system, that is influenced by constraints from the primary datum and the secondary datum in the datum system
3.8
single datum
datum established from one datum feature taken from a single surface or from one feature of size
Note 1 to entry: The invariance class of a single surface can be complex, prismatic, helical, cylindrical, revolute, planar or spherical. A set of situation features defining the datum (see Table B.1) corresponds to each type of single surface.
3.9
common datum
datum established from two or more datum features considered simultaneously
Note 1 to entry: To define a common datum, it is necessary to consider the collection surface created by the considered datum features. The invariance class of a collection surface can be complex, prismatic, helical, cylindrical, revolute, planar or spherical (see Table B.1).
3.10
datum system
set of two or more situation features established in a specific order from two or more datum features
Note 1 to entry: To define a datum system, it is necessary to consider the collection surface created by the considered datum features. The invariance class of a collection surface can be complex, prismatic, helical, cylindrical, revolute, planar or spherical (see Table B.1).
3.11
datum target
portion of a datum feature which can nominally be a point, a line segment or an area
Note 1 to entry: Where the datum target is a point, a line or an area, it is indicated as a datum target point, a datum target line or a datum target area, respectively.
3.12
moveable datum target
datum target with a controlled motion
3.13
collection surface
two or more surfaces considered simultaneously as a single surface
Note 1 to entry: Table B.1 is used to determine the invariance class of a datum or datum systems when using a collection of surfaces.
Note 2 to entry: Two intersecting planes may be considered together or separately. When the two intersecting planes are considered simultaneously as a single surface, that surface is a collection surface.
3.14
objective function
<association> formula that describes the goal of association from the datum feature and the ideal feature (associated feature)
Note 1 to entry: In this document, the term “objective function” refers to “objective function for association”.
Note 2 to entry: The objective functions are usually named and mathematically described: maximum inscribed, minimum zone, etc.
[SOURCE: ISO 4351:2023, 3.6, modified — “datum feature” replaced “input feature”. Notes to entry added.]
3.15
constraint
set of restrictions on variability of the mathematical parameters describing an associated feature (3.3) in the optimization process
EXAMPLE        Orientation constraint, location constraint, material constraint or intrinsic characteristic constraint are the different types of constraint.
[SOURCE: ISO 4351:2023, 3.9, modified — “constraint” replaced “association constraint” as the term and in the example. “intrinsic characteristic constraint” replaced “size constraint” in the example.]
3.15.1
orientation constraint
constraint (3.15) related to one or more rotational degrees of freedom of associated feature (3.3)
[SOURCE: ISO 4351:2023, 3.10, modified — “constraint” replaced “association constraint”.]
3.15.2
location constraint
constraint (3.15) related to one or more translational degrees of freedom of associated feature (3.3)
[SOURCE: ISO 4351:2023, 3.11, modified — “constraint” replaced “association constraint”.]
3.15.3
material constraint
constraint (3.15) on the associated feature (3.3), in relation to the material boundary of the datum feature (3.2)
EXAMPLE        The outside material constraint implies that all distances between the associated feature and the datum feature are negative or equal to zero.
[SOURCE: ISO 4351:2023, 3.12, modified — “constraint” replaced “association constraint” and “datum feature” replaced “input feature”.]
3.15.4
intrinsic characteristic constraint
size constraint
association constraint (3.15) on an intrinsic characteristic of associated feature (3.3) whether it is considered fixed or variable
Note 1 to entry: The intrinsic characteristic of a cylinder is its diameter which is a size.
Note 2 to entry: In the collection surface, constituted by two parallel and not coaxial cylinders, there are more than one intrinsic characteristic (two diameters, the distance between their axes and the angle of 0°).
3.16
association criterion
objective function with or without constraints, defined for an association
Note 1 to entry: Several constraints may be defined for an association.
Note 2 to entry: Association results (associated features) may differ, depending upon the choice of association criterion.
Note 3 to entry: Default association criteria are defined in Annex A.
3.17
integral feature
surface or line on a surface
Note 1 to entry: An integral feature is intrinsically defined.
3.18
contacting feature
ideal feature of any type which is different from the nominal feature under consideration and is associated with the corresponding datum feature
Note 1 to entry: See Figure 1.
Figure 1 — Example of a contacting feature
graphic
graphic
a) Contacting feature on nominal model b) Contacting feature on real workpiece
Key
1 contacting feature: ideal sphere in contact with the datum feature or the feature under consideration
2 features under consideration: nominal trapezoidal slot (collection of two non-parallel surfaces)
3 datum feature: real feature corresponding to the trapezoidal slot (collection of two non-parallel surfaces)
3.19
invariance class
group of ideal features for which the nominal surface is invariant for the same degrees of freedom
Note 1 to entry: There are seven invariance classes (see Annex B).
3.20
datum coordinate system
coordinate system established from a single datum, a common datum or a datum system
Note 1 to entry: Using a datum coordinate system is optional.
3.20.1
datum coordinate system indicator
indication defining a coordinate system
3.20.2
datum coordinate system identifier
label identifying a coordinate system
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Bibliography
[1]
ISO 2768-1, General tolerances — Part 1: Tolerances for linear and angular dimensions without individual tolerance indications
[2]
ISO 5456-1, Technical drawings — Projection methods — Part 1: Synopsis
[3]
ISO 5459:1981,4 Technical drawings — Geometrical tolerancing — Datums and datum-systems for geometrical tolerances
[4]
ISO 5459:2011,5 Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems
[5]
ISO 7083, Technical product documentation — Symbols used in technical product documentation — Proportions and dimensions
[6]
ISO 8015, Geometrical product specifications (GPS) — Fundamentals — Concepts, principles and rules
[7]
ISO 14253-1, Geometrical product specifications (GPS) — Inspection by measurement of workpieces and measuring equipment — Part 1: Decision rules for verifying conformity or nonconformity with specifications
[8]
ISO 14638, Geometrical product specifications (GPS) — Matrix model
[9]
ISO 16610 (all parts), Geometrical product specifications (GPS) — Filtration
[10]
ISO 81714-1, Design of graphical symbols for use in the technical documentation of products — Part 1: Basic rules
[11]
Shakarji, C.M., Srinivasan, V. Theory and algorithm for planar datum establishment using constrained total least-squares. Procedia CIRP. 2016, 43 pp.232–237
[12]
Shakarji, C.M., Srinivasan, V. Toward a new mathematical definition of datums in standards to support advanced manufacturing. In: International Manufacturing Science and Engineering Conference (Vol. 51371, p. V003T02A016). American Society of Mechanical Engineers, 2018
[13]
Shakarji, C.M., Srinivasan, V. Toward a New Mathematical Definition of Datums in Standards to Support Advanced Manufacturing. Journal of Computing and Information Science in Engineering. 2023, 23(2) p.021013
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4 Cancelled and replaced by ISO 5459:2011.
5 Cancelled and replaced by this document.