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Ref. No,: ISO/R129-I959(E)
IS0
I NT ER NAT1 O NA L ORGAN I Z AT10 N FOR S TA N DARD I ZATl O N
IS0 RECOMMENDATION
R 129
ENGINEERING DRAWING
DlMENSlONlNG
1st EDITION
September 1959
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
I
Printed in Switzerland
Copies to be obtained through the national standards organizations.
Also issued in French and Russian.
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BRIEF HISTORY
The IS0 Recommendation R 129, Engineering Drawing - Dimensioning, was
drawn up by Technical Committee ISO/TC 10, Drawings (General Principles), the Secre-
tariat of which is held by the Association Suisse de Normalisation (SNV).
During its first meeting, held in Zurich, in September 1951, the Technical Committee
decided to use as the basis for its work the ISA Bulletin No. 32, drawn up by the former
International Federation of the National Standardizing Associations (ISA). The develop-
ment of the various drafts was entrusted to Sub-Committee SC 1, Preliminary work, com-
prising Austria, Belgium, France, Italy, Netherlands, Sweden, Switzerland, United
Kingdom and, since 1952, Germany.
After six meetings spaced over the years 1952, 1953 and 1954, the Sub-Committee
submitted to the plenary Technical Committee three proposals relative to the dimen-
sioning of engineering drawings, namely : 1) General principles, 2) Method of execution,
3) Arrangement of dimensions. At its second meeting, held in Stockholm, in June
and
1955, the Technical Committee adopted these three proposals as Draft IS0 Recommenda-
tions.
On 31 December 1956, these three Draft IS0 Recommendations were distributed
to all the IS0 Member Bodies and were approved, subject to a certain number of modifi-
cations, by the following 19 (out of a total of 38) Member Bodies:
Australia Germany Norway
Austria "Greece Pakistan
*Brazil Italy Spain
Canada Japan Switzerland
Denmark Mexico Turkey
Finland Netherlands U.S.S.R.
France
The Draft covering general principles was, furthermore, approved by the Member
Bodies of Bulgaria, Romania and the Union of South Africa. The Draft dealing with
the method of execution was, furthermore, approved by the Member Body of Israel. The
Draft concerning the arrangement of dimensions was, furthermore, approved by the Mem-
ber Bodies of Belgium, Bulgaria, Israel and Portugal.
No Member Body opposed the approval of the Drafts.
These three Draft IS0 Recommendations were then submitted, by correspondence,
to the IS0 Council, which decided, in September 1959, to accept them as IS0 RECOM-
MENDATIONS.
In line with a suggestion made by a Member of the Editing Committee, it was decided
to group into a single IS0 Recommendation the subject-matter of the three Draft IS0
Recommendations.
The simplest possible figures have been chosen to illustrate the text. Some figures
are so clear that they need no comment. The explanatory texts allow these principles to
be adopted to those more complicated situations which arise in practice.
* These Member Bodies stated that they had no objection to the Drafts being approved.
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TABLE OF CONTENTS
Page
Introductory Note . 4
1 . General principles . 4
1.1 Definitions . 4
1.2 Principles . 5
2 . Method of execution . 7
2.1 Projection lines and dimension lines . 7
2.2 Arrows . 9
2.3 Inscription of dimensions . 10
2.4 Addition of letters and symbols . 12
2.5 Special indications . 13
3 . Arrangement of dimensions . 14
3.1 Chain dimensioning . 14
3.2 Parallel dimensioning . 14
3.3 Combined dimensioning . 15
3.4 Dimensioning by co-ordinates . 15
3.5 Chamfers . 15
3.6 Equal dimensions . 16
3.7 Equidistant features . 16
3.8 Assembled parts . 16
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IS0 Recommendation R 129 September 1959
ENGINEERING DRAWING
DlMENSlONlNG
INTRODUCTORY NOTE
For uniformity all the dimensions in this IS0 Recommendation are given in
metric units only and the figures are in European (First angle) projection. It
should be understood that inch units and/or American (Third angle) projection
could equally well have been used without prejudice to the principles established.
1. GENERAL PRINCIPLES
1.1 Definitions
The following definitions apply to the terms used in the IS0 Recommendations
relating to engineering drawings.
1.1.1 End product drawing. An end product drawing provides a complete
description of the product in the condition in which it is to be used, those
requirements essential to the function of the product being expressed
directly on the drawing. The product may be a piece ready for assembly
or service, or a piece for further processing (e.g. the product of a foundry
or forge).
1.1.2 Feature. A feature is an individual characteristic of a piece, such as a
cylindrical surface, shoulder, screw thread, slot, flat surface, profile or the
like.
1.1.3 Functional feature. A functional feature is a feature which plays an
essential part in the performance or serviceability of the piece to which
it belongs. It may be a location feature, e.g. a spigot which serves to
locate a component in an assembly, or a working surface, e.g. the bore
of a bearing.
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ISO/R 129 - I959 (E)
1.1.4 Functional dimension.
A functional dimension is a dimension which is
essential to the function of a product (Fig. 1).
F _,_ F
F",
* Minimum length of
full thread
(Aux)
Fig. I
F = a functional dimension
NF = a non-functional dimension
Aux = an auxiliary dimension given without tolerance, for information
only.
1.2 Principles
1.2.1 All the dimensions and tolerances, etc., necessary to provide for the correct
functioning of the part should be expressed directly on the drawing together
with any other information necessary to describe the part completely in its
finished form, without forgetting the manufacturing and inspection require-
ments.
No single dimension should be given more than once on the drawing, except
where unavoidable.
It should not be necessary to deduce a functional dimension from other
dimensions or to scale the drawing.
Dimensions should be placed on the view which shows the relevant features
most clearly.
All dimensions on a drawing should be given in the same unit, for instance,
in millimetres, otherwise the unit should be indicated after the dimensions.
1.2.2 No more dimensions should be given than are necessary to describe the end
product, nor should any feature be located by more than one toleranced
dimension in any one direction.
Exception may however be made in the following circumstances:
(a) In special cases, where it is necessary to give dimensions which apply
at intermediate stages of manufacture, e.g. for the size of a feature
before carburizing and finishing to size.
(b) Where it is desirable to add auxiliary dimensions which, although not
essential for the complete definition of the end product, provide useful
information which may avoid the need for calculation by workmen
and others. Such auxiliary dimensions are not toleranced, and where
general tolerances apply, these auxiliary dimensions should be enclosed
in brackets (Fig. 1) to show that they are not subject to these tolerances
and do not control the acceptability of the part in any way.
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1.2.3 The functional dimensions should be expressed directly on the drawing
1 and 2). To do otherwise (Fig. 3) necessitates a redistribution of
(Fig.
the tolerances, with the general result that tighter tolerances are required
to maintain the functional requirements. This does not preclude the
dimensioning of holes centre to centre, although the functional dimension
may be edge to edge.
2520.06 -IA 15t0.01
Fig. 2 Fig. 3
Tolerances have hod to be reduced
to ensure that function is sofe-
guarded.
f.2.4 The non-functional dimensions should be placed in the manner most
convenient to the producer or inspector.
1.2.5 Tolerances should be specified for all requirements affecting functioning
or interchangeability unless ordinary or established workshop practice
guarantees the required standard of accuracy. Tolerances should also be
used where unusually wide variations are permissi
...