EN ISO 5459:2024

SLOVENSKI STANDARD
01-december-2024
Specifikacija geometrijskih veličin izdelka - Geometrijsko toleriranje - Reference in
sistemi referenc (ISO 5459:2024)
Geometrical product specifications (GPS) - Geometrical tolerancing - Datums and datum
systems (ISO 5459:2024)
Geometrische Produktspezifikation (GPS) - Geometrische Tolerierung - Bezüge und
Bezugssysteme (ISO 5459:2024)
Spécification géométrique des produits (GPS) - Tolérancement géométrique -
Références spécifiées et systèmes de références spécifiées (ISO 5459:2024)
Ta slovenski standard je istoveten z: EN ISO 5459:2024
ICS:
17.040.10 Tolerance in ujemi Limits and fits
17.040.40 Specifikacija geometrijskih Geometrical Product
veličin izdelka (GPS) Specification (GPS)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 5459
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2024
EUROPÄISCHE NORM
ICS 17.040.40 Supersedes EN ISO 5459:2011
English Version
Geometrical product specifications (GPS) - Geometrical
tolerancing - Datums and datum systems (ISO 5459:2024)
Spécification géométrique des produits (GPS) - Geometrische Produktspezifikation (GPS) -
Tolérancement géométrique - Références spécifiées et Geometrische Tolerierung - Bezüge und
systèmes de références spécifiées (ISO 5459:2024) Bezugssysteme (ISO 5459:2024)
This European Standard was approved by CEN on 27 July 2024.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 5459:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 5459:2024) has been prepared by Technical Committee ISO/TC 213
"Dimensional and geometrical product specifications and verification" in collaboration with Technical
Committee CEN/TC 290 “Dimensional and geometrical product specification and verification” the
secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2025, and conflicting national standards shall be
withdrawn at the latest by April 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 5459:2011.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 5459:2024 has been approved by CEN as EN ISO 5459:2024 without any modification.

International
Standard
ISO 5459
Third edition
Geometrical product specifications
2024-10
(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) © ISO 2024
ISO 5459:2024(en)
© ISO 2024
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 5459:2024(en)
Contents Page
Foreword .v
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 5
5 Role of datums . 7
6 General concepts . 9
6.1 General .9
6.2 Intrinsic characteristics of surfaces associated with datum features .10
6.2.1 General .10
6.2.2 Single datum established from a single feature .11
6.2.3 Common datum established from two or more single features simultaneously .11
6.2.4 Datum systems established in a defined sequence from two or more single
features . 13
6.3 Single datums, common datums and datum systems . 13
6.3.1 General . 13
6.3.2 Single datums . 13
6.3.3 Common datums . .14
6.3.4 Datum systems. 15
7 Graphical language .18
7.1 General .18
7.2 Indication of datum features .18
7.2.1 Datum feature indicator .18
7.2.2 Datum feature identifier.19
7.2.3 Datum targets .19
7.3 Specification of datums and datum systems . 23
7.4 Indication and meaning of rules .24
7.4.1 General .24
7.4.2 Rules .24
8 Specification operators for datum .47
8.1 ISO default specification operator for datum .47
8.2 Special specification operator for datum .47
8.2.1 General .47
8.2.2 Filtration specification elements for datum . 48
8.2.3 Association specification elements for datum . 49
8.3 Drawing-default specification operator for datums . 50
Annex A (normative) Association for datums . .51
Annex B (informative) Invariance classes . 61
Annex C (informative) Examples .63
Annex D (informative) Former practices .86
Annex E (informative) Examples of a datum system or a common datum established with
contacting features .90
Annex F (normative) Relations and dimensions of graphical symbols .96
Annex G (normative) Establishment of a datum coordinate system from a datum system .99
Annex H (informative) Filter symbols and attached nesting index .103
Annex I (informative) Issue of orientation and location constraints in datum systems .104

iii
ISO 5459:2024(en)
Annex J (normative) Filtration of a datum feature which is nominally a plane .111
Annex K (informative) Relation to the GPS matrix model .114
Bibliography .115

iv
ISO 5459:2024(en)
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;

v
ISO 5459:2024(en)
— 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.

vi
ISO 5459:2024(en)
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.
vii
International Standard ISO 5459:2024(en)
Geometrical product specifications (GPS) — Geometrical
tolerancing — Datums and datum systems
1 Scope
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.
NOTE The detailed rules for maximum and least material requirements for datums are given in ISO 2692.
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 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
3 Terms 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

ISO 5459:2024(en)
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.

ISO 5459:2024(en)
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
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.]

ISO 5459:2024(en)
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.

ISO 5459:2024(en)
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)
Figure 1 — Example of a contacting feature
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
4 Symbols
Table 1 gives symbols to identify the datum feature and datum target used to establish a datum.
Table 2 gives the list of modifier symbols, which can be associated the datum identifier.

ISO 5459:2024(en)
Table 1 — Datum features and datum target symbols
Description Symbol Sub-
clause
Datum feature indicator 7.2.1
Datum feature identifier Capital letter (A, B, C, AA, etc.) 7.2.2
Single datum target frame 7.2.3.2
Moveable datum target frame 7.2.3.2
a
Single datum target indicator 7.2.3
Moveable datum target
7.2.3
a
indicator
Datum target point 7.2.3.3
Closed datum target line 7.2.3.3
Non-closed datum target line 7.2.3.3
Datum target area 7.2.3.3
Restricted datum feature 7.4.2.4
a
The terminator of the leader line is dependent of the type of datum target.

ISO 5459:2024(en)
TTaabblle 1 e 1 ((ccoonnttiinnueuedd))
Description Symbol Sub-
clause
Indication of a situation feature
of a single datum, a common 7.4.2.12
datum or a datum system
For single datum For datum system
Datum coordinate system indi-
Annex G
cator
a
The terminator of the leader line is dependent of the type of datum target.
Table 2 — Modifier symbols
Symbol Description Subclause
[PD] Pitch diameter 7.4.2.1
[MD] Major diameter 7.4.2.1
[LD] Minor diameter 7.4.2.1
[ACS] Any cross-section 7.4.2.4
[ALS] Any longitudinal section 7.4.2.4
[CF] Contacting feature 7.4.2.5
[SV] Size, variable 7.4.2.2
[SF] Size, fixed 7.4.2.2
[SFxx] Size, fixed with specified value xx 7.4.2.2
[DV] Distance, variable (for common datum) 7.4.2.7
[PT] (situation feature of type) point 7.4.2.8
[SL] (situation feature of type) straight line 7.4.2.8
[PL] (situation feature of type) plane 7.4.2.8
>< For orientation constraint only 7.4.2.8
Projected (for secondary or tertiary datum)
7.4.2.10
Least material requirement
See ISO 2692
Maximum material requirement
See ISO 2692
NOTE  Other symbols related to filtration and association are presented in Tables 8 to 10 and in Table H.1.
5 Role of datums
Datums form part of a geometrical specification (see ISO 1101).
Datums are established from real surfaces identified on a workpiece.

ISO 5459:2024(en)
Datums allow tolerance zones to be located or orientated (see Examples 1 and 2) and virtual conditions to
be defined (for example maximum material virtual condition according to ISO 2692). The datums can be
seen as a means to lock degrees of freedom of a tolerance zone. The number of degrees of freedom of the
tolerance zone which are locked depends on the nominal shape of the features utilized to establish the datum
or datum system; whether the datum is primary, secondary or tertiary; and on the toleranced characteristic
indicated in the geometrical tolerance frame.
By default, a datum locks all the degrees of freedom of the tolerance zone that it can lock given its shape and
which
— are required by the geometrical characteristic indicated in the tolerance frame, and
— have not already been locked by the preceding datum(s) in the datum system.
When a datum locks only orientation degrees of freedom, this shall be indicated by the modifier >< .
EXAMPLE 1 The tolerance zone, which is the space between two parallel planes 0,1 mm apart, is constrained in
orientation by a 75° theoretically exact angle from the datum. Here, the datum is the situation feature of a cylinder
(axis of associated cylinder). See Figure 2.
Dimensions in millimetres
a) Indication on the drawing b) Illustration of tolerance zone
Key
1 datum A constituted by the axis of the associated cylinder
Figure 2 — Example of tolerance zone constrained in orientation from a datum
EXAMPLE 2 The tolerance zone, which is the space between two parallel planes 0,2 mm apart, is constrained
in orientation by a 70° angle from a datum, and in location by the distance 20 mm from the gauge plane positioned
perpendicular to the axis of 40° cone where its local diameter is 30 mm. Here, the datum consists of the set of situation
features of the cone with a fixed angle of 40°, i.e. the cone axis and the point of intersection between the gauge plane
and that axis. See Figure 3.
ISO 5459:2024(en)
Dimensions in millimetres
a) Indication on the drawing b) Illustration of tolerance zone
Key
1 datum A constituted by the axis of the associated cone, the point of intersection of the gauging plane and this axis
Figure 3 — Example of a tolerance zone constrained in location from a datum
6 General concepts
6.1 General
Datums and datum systems are theoretically exact geometric features used together with implicit or explicit
TEDs to locate or orientate
a) tolerance zones for toleranced features, or
b) virtual conditions, e.g. in the case of maximum material requirement (see ISO 2692).
A datum consists of a set of situation features for an ideal feature (feature of perfect form). This ideal feature
is an associated feature which is established from the identified datum features of a workpiece. Datum
features can be complete features, or identified portions thereof (see Clause 7).
A datum system consists of more than one datum.
The geometrical type of these associated features belongs to one of the following invariance classes:
— spherical (i.e. a sphere);
— planar (i.e. a plane);
— cylindrical (i.e. a cylinder);

ISO 5459:2024(en)
1)
— helical (e.g. a threaded surface) ;
— revolute (e.g. a cone or a torus);
— prismatic (e.g. a prism);
— complex (e.g. a free-form surface).
Each single or collection feature belongs to one invariance class (for an explanation of invariance classes,
invariance degree, and degree of freedom, see Annex B).
Associated features are established from the real or extracted single features used for the datum. The
associated feature can be defined by an operation of association including constraints coming from the
feature itself or from one or more other features. The situation features that make up the datum are defined
from these associated features. The default association methods are given in Annex A.
One or more single features can be used to establish a datum. If only one single feature is used, it establishes
a single datum. If more than one single feature is used, they can either be considered simultaneously to
establish a common datum or in a predefined order to establish a datum system (see 6.3).
The datum feature(s) to be used for establishing each datum shall be designated and identified.
The single datums (see 6.3.2), common datums (see 6.3.3) or datum systems (see 6.3.4), as applicable, shall
be specified for each geometrical specification.
When applicable, any additional constraints shall be defined for the association.
Datums and datum systems are situation features, not coordinate systems. The set of situation feature is
established in a process including associations, but can also include some other geometrical operations (e.g.
intersection, translation, rotation). A complete datum system (allowing to lock all six degrees of freedom)
is a set of one point, one straight line and one plane (the point on the straight line in the plane). Coordinate
systems can be established from a datum or a datum system that locks all six degrees of freedom. In this
case, it shall be indicated in accordance with Annex G.
EXAMPLE In Figure 4, the datum is indicated as a single datum derived from a nominal feature, a cylinder, used to
orientate or locate a tolerance zone. In order to derive the datum, the following sequence of operations is performed:
— a partition to define the real integral surface corresponding to the nominal feature [see Figure 4 b)];
— an extraction to provide the extracted integral feature [see Figure 4 c)];
— a filtration (see Annex A);
— an association (see Annex A for association method) to define the associated feature. (In this case, its type is the
same as the nominal feature.) The associated feature [see Figure 4 d)] is established from the non-ideal surface (in
the specification process) or from the extracted feature (in the verification process).
The datum is defined as the situation feature (the axis) of the associated cylinder [see Figure 4 e)].
6.2 Intrinsic characteristics of surfaces associated with datum features
6.2.1 General
The default status (variable or fixed) of the intrinsic characteristics is described in 6.2.2, 6.2.3 or 6.2.4. For
rules, see also rule 2 (2A to 2D) in 7.4.2.2.
For datums with virtual conditions, see ISO 2692.
Issues of orientation and location constraints in datum systems are presented in Annex I.
1) Helical surfaces as such are not considered in this document. They are regarded as cylindrical surfaces because,
in most functional cases where helical surfaces (threads, helical slope, endless screw, etc.) are involved, the combined
rotation and translation of the helix is not needed for datum purposes. In these cases, the pitch cylinder surface is used to
establish the datum. The major or minor cylindrical surface can also be considered and specified.

ISO 5459:2024(en)
6.2.2 Single datum established from a single feature
The default status of the intrinsic characteristics for a single feature is:
— variable for the linear size of a feature of size (see Table 3);
— fixed for the angular size of a feature of size (see Table 3);
— fixed for an intrinsic characteristic which is not the linear size of a feature of size.
Table 3 — Default status of intrinsic characteristics of features of size
Feature of size Invariance class Intrinsic characteristic Default status
Variable
Cylinder Cylindrical Diameter
See example in C.2.2
Variable
Sphere Spherical Diameter
See example in C.2.4
Variable
Two parallel opposite planes Planar Distance between the two planes
See example in C.2.10
Fixed
Cone Revolute Angle
See example in C.2.3
Fixed
Wedge Prismatic Angle
See example in C.2.9
6.2.3 Common datum established from two or more single features simultaneously
The default status (variable or fixed) of the intrinsic characteristics of each associated feature establishing
the common datum is as in 6.2.2.
Intrinsic characteristics introduced by the collection of features (defining the relation between the associated
features) shall by default be considered theoretically exact for both linear and angular dimensions.

ISO 5459:2024(en)
a) Drawing  b) Integral real  c) Extraction
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