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INTERNATIONAL ISO
STANDARD 128-3
First edition
2020-06
Technical product documentation

(TPD) — General principles of
representation —
Part 3:
Views, sections and cuts
Documentation technique
iTeh STANDARD PREVIEW de produits (TPD) — Principes généraux de
représentation —
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Partie 3: Vues, sections et coupes
ISO 128-3:2020
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5df5790a32a0/iso-128-3-2020
Reference number
ISO 128-3:2020(E)
© ISO 2020
ISO 128-3:2020(E)

iTeh STANDARD PREVIEW

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ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
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ISO 128-3:2020(E)

Contents Page
Foreword......................................................................................................................................................................................................................................... iv
Introduction...................................................................................................................................................................................................................................v
1 Scope.................................................................................................................................................................................................................................. 1
2 Normative references....................................................................................................................................................................................... 1
3 Terms and definitions...................................................................................................................................................................................... 1
4 Basic conventions for views....................................................................................................................................................................... 2
4.1 General information on views.................................................................................................................................................... 2
4.2 Choice of views........................................................................................................................................................................................ 3
4.3 Partial views............................................................................................................................................................................................... 3
4.4 Simplified view of symmetrical parts................................................................................................................................... 4
4.5 First angle projection method.................................................................................................................................................... 4
4.6 First angle projection method views.................................................................................................................................... 4
4.7 First angle projection graphical symbol............................................................................................................................. 5
4.8 Third angle projection method.................................................................................................................................................. 5
4.9 Third angle projection method views.................................................................................................................................. 5
4.10 Third angle projection graphical symbol.......................................................................................................................... 6
4.11 Other projection methods.............................................................................................................................................................. 6
4.12 Enlarged features................................................................................................................................................................................... 6
5 Reference indication for views and enlarged features.................................................................................................. 7
5.1 iTeh STANDARD PREVIEW
General............................................................................................................................................................................................................ 7
5.2 Details of the reference indication.......................................................................................................................................... 7
5.3
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Examples of indication...................................................................................................................................................................... 8
6 General information on cuts andISO sections128-3:2020 .................................................................................................................................. 9
6.1 General ............................................................................................................................................................................................................ 9
6.2 Indication of cuts and5df5790a32a0/iso-128-3-2020
sections................................................................................................................................................... 9
6.2.1 Cutting plane........................................................................................................................................................................ 9
6.2.2 Identification of the cutting plane..................................................................................................................... 9
6.2.3 Identification of the cuts and sections........................................................................................................... 9
6.2.4 Reference indication for cuts and sections............................................................................................. 10
6.3 Sections revolved in the relevant view............................................................................................................................. 11
6.4 Cuts/sections of symmetrical parts.................................................................................................................................... 12
6.5 Local cuts/sections............................................................................................................................................................................ 12
7 Basic conventions for representing areas on cuts and sections.......................................................................13
7.1 General information on cuts and sections..................................................................................................................... 13
7.2 Hatching...................................................................................................................................................................................................... 13
7.3 Shading or toning................................................................................................................................................................................ 14
7.4 Extra-wide continuous outlines............................................................................................................................................. 15
7.5 Thin sections........................................................................................................................................................................................... 15
7.6 Thin adjacent sections.................................................................................................................................................................... 15
7.7 Specific materials................................................................................................................................................................................ 16
Annex A (normative) Graphical symbols.......................................................................................................................................................17
Annex B (informative) Former practices........................................................................................................................................................20
Annex C (normative) Views on mechanical engineering technical drawings..........................................................22
Annex D (normative) Sections on mechanical engineering technical drawings...................................................34
Annex E (normative) Projection methods in building technical drawings.................................................................39
Annex F (normative) Representation of views, sections and cuts on construction drawings................41
Bibliography.............................................................................................................................................................................................................................. 48
© ISO 2020 – All rights reserved iii

ISO 128-3:2020(E)

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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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. (standards.iteh.ai)
This document was prepared by Technical Committee ISO/TC 10, Technical product documentation, in
collaboration with the European Committee forISO 128-3:2020
Standardization (CEN) Technical Committee CEN/SS
F01, Technical drawings, in accordance with the Agreement on technical cooperation between ISO and
CEN (Vienna Agreement). 5df5790a32a0/iso-128-3-2020
This first edition cancels and replaces the following documents:

— ISO 128-30:2001
— ISO 128-33:2018
— ISO 128-34:2001
— ISO 128-40:2001
— ISO 128-44:2001
— ISO 128-50:2001
The main changes to these documents are as follows:
— harmonization of the former parts listed above;
— introduction of reference indication for views and enlarged features;
— use of arc arrow in special position of views moved to a former practice annex.
A list of all parts in the ISO 128 series can be found on the ISO website.
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.
iv © ISO 2020 – All rights reserved

ISO 128-3:2020(E)

Introduction
This document contains generally applicable rules for the presentation of views, sections and cuts in all
kinds of technical product documentation. The first angle projection method (formerly referred to as
method E) and the third angle projection method (formerly referred to as method A) are described in
more detail in ISO 5456-2.
All figures in this document, excluding Figure 1, Figure 6 and Figure 7, have been drawn in first-angle
projection method unless other methods are stated. It should be understood that third-angle projection
or other methods could have been used equally well without prejudice to the principles established.
The application of views, sections and cuts within drawings of special technical fields varies
considerably. Therefore, rules of application specific to technical fields are given in Annex A, B and C.

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ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
© ISO 2020 – All rights reserved v

(standards.iteh.ai)
ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
INTERNATIONAL STANDARD ISO 128-3:2020(E)
Technical product documentation (TPD) — General

principles of representation —
Part 3:
Views, sections and cuts
1 Scope
This document specifies the general principles for presenting views, sections and cuts applicable to
various kinds of technical drawings (e.g. mechanical, electrical, architectural, civil engineering),
following the orthographic projection methods specified in ISO 5456-2. Views and sections for
shipbuilding technical drawings are discussed in ISO 128-15. Views and sections for 3D models are
discussed in ISO 16792.
Attention has also been given in this document to the requirements of reproduction, including
microcopying in accordance with ISO 6428.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
(standards.iteh.ai)
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 128-3:2020
ISO 128-2:—1), Technical drawings — General principles of presentation — Part 2: Basic conventions for lines
5df5790a32a0/iso-128-3-2020
ISO 129-1, Technical product documentation (TPD) — Presentation of dimensions and tolerances — Part 1:
General principles
ISO 3098-1, Technical product documentation — Lettering — Part 1: General requirements
ISO 5456-2, Technical drawings — Projection methods — Part 2: Orthographic representations
ISO 6428, Technical drawings — Requirements for microcopying
ISO 10209:2012, Technical product documentation — Vocabulary — Terms relating to technical drawings,
product definition and related documentation
ISO 15519-1, Specification for diagrams for process industry — Part 1: General rules
ISO 81714-1, Design of graphical symbols for use in the technical documentation of products — Part 1:
Basic rules
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 10209 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://w ww.iso.org/obp
— IEC Electropedia: available at http://w ww.electropedia.org/
1) Under preparation. Stage at the time of publication: ISO/FDIS 128-2:2020.
© ISO 2020 – All rights reserved 1

ISO 128-3:2020(E)

3.1
cut
sectional view
section (3.2) showing, in addition, outlines beyond the cutting plane
Note 1 to entry: While “cut” is generally used in the construction field, “section” is generally used in the
mechanical engineering field, regardless of the definitions in 3.1 or 3.2.
[SOURCE: ISO 10209:2012, 3.11, modified — Note 1 to entry added.]

3.2
section
representation showing only the outlines of an object lying in one or more cutting planes
Note 1 to entry: While “cut” is generally used in the construction field, “section” is generally used in the
mechanical engineering field, regardless of the definitions in 3.1 or 3.2.
[SOURCE: ISO 10209:2012, 3.61, modified — Note 1 to entry added.]

3.3
technical drawing
drawing showing a technical installation, process or product with a view to clarifying its structure and
enabling its construction
Note 1 to entry: For the purpose of this document, the term “technical drawing” is interpreted in the broadest
possible sense, encompassing the total package of documentation specifying the product (work piece,
subassembly, assembly). iTeh STANDARD PREVIEW
[SOURCE: ISO 5127:2017, 3.4.7.54, modified — Note 1 to entry added.]
(standards.iteh.ai)
4 Basic conventions for views ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
4.1 General information on views
The most informative view of an object shall be used as the principle view, taking into consideration, for
example, its functioning position, position of manufacturing or mounting.
Each view, with the exception of the front or principal figure (view, plan, principal figure), shall be
given clear identification with a capital letter, repeated near the reference arrow needed to indicate the
direction of viewing for the relevant view. Whatever the direction of viewing, the capital letter shall
always be positioned in normal relation to the direction of reading and be indicated either above or on
the right side of the reference arrow.
The reference arrow is defined in Annex A (for the former practice of arc arrow, see Annex B), as is the
lettering height of the identification.
The designated views may be located irrespective of the principal figure. The capital letters identifying
the referenced views shall be placed immediately above the relevant views (see Figure 1).
2 © ISO 2020 – All rights reserved

ISO 128-3:2020(E)

Figure 1 — Identification of referenced views

For applying views and sections to mechanical engineering technical drawings, Annex C and Annex D
(standards.iteh.ai)
shall apply. For applying projection methods in building technical drawings, Annex E shall apply. For
applying views, sections and cuts to construction technical drawings, Annex F shall apply.
ISO 128-3:2020
4.2 Choice of views 5df5790a32a0/iso-128-3-2020
When views (including cuts and sections) are needed, these shall be selected according to the following
principles:
— limit the number of views (and cuts and sections) to the minimum necessary but sufficient to fully
delineate the object without ambiguity;
— avoid the need for hidden outlines and edges;
— avoid unnecessary repetition of a detail.
Views and sections for 3D models are given in ISO 16792.
4.3 Partial views

Features needing specific illustration, but not meriting a full view, can be illustrated using a partial view
limited by a continuous narrow line with zigzags of type 01.1 according to ISO 128-2:— (see Figure 2).

ISO 128-3:2020(E)

Figure 2 — Partial view
4.4 Simplified view of symmetrical parts

To save time and space, symmetrical objects can be drawn as a fraction of the whole [see Figure 3 a), b)
and c)].
The line of symmetry is identified at each of its ends by two narrow short parallel lines drawn at right
angles to it [see Figure 3 a), b) and c)]. The graphical symbol for symmetry shall be drawn in accordance
with A.3.

(standards.iteh.ai)
ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
a) Example 1 b) Example 2 c) Example 3
Figure 3 — Examples of simplified views of symmetrical parts
4.5 First angle projection method

The first angle projection method, if used, shall be in accordance with ISO 5456-2.
4.6 First angle projection method views

With reference to the front view, (a), the other views are arranged as follows (see Figure 4):
— the view from above, (b), is placed underneath;
— the view from below, (e), is placed above;
— the view from the left, (c), is placed on the right;

ISO 128-3:2020(E)

— the view from the right, (d), is placed on the left;

— the view from the rear, (f), may be placed on the left or right, as convenient.
Figure 4 — First angle projection method

4.7 First angle projection graphical symbol
(standards.iteh.ai)
The graphical symbol for the first angle projection method is shown in Figure 5. The proportions and
dimensions of this graphical symbol are specified in ISO 5456-2.
ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
Figure 5 — First angle projection graphical symbol
4.8 Third angle projection method

The third angle projection method, if used, shall be in accordance with ISO 5456-2.
4.9 Third angle projection method views

With reference to the front view, (a), the other views are arranged as follows (see Figure 6):
— the view from above, (b), is placed above;
— the view from below, (e), is placed underneath;
— the view from the left, (c), is placed on the left;
— the view from the right, (d), is placed on the right;
— the view from the rear, (f), may be placed on the left or right, as convenient.

ISO 128-3:2020(E)

Figure 6 — Third angle projection method
4.10 Third angle projection graphical symbol

The graphical symbol for the third angle projection method is shown in Figure 7. The proportions and
dimensions of this graphical symbol are specified in ISO 5456-2.
(standards.iteh.ai)
ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
Figure 7 — Third angle projection graphical symbol
4.11 Other projection methods

Refer to ISO 5456-2 for information on other projection methods such as mirrored orthographic
projections.
4.12 Enlarged features

When the scale of a technical drawing does not allow all features to be clearly shown or dimensioned,
the unclear features shall be enclosed or encircled by a continuous narrow line (type 01.1), with the area
thus enclosed identified by a capital letter. The features in the area shall also be shown on an enlarged
scale, in a view that is broken with a continuous narrow freehand/free formed curve line (type 01.1).
This shall be accompanied by the identification letter and an indication of the scale beside it between
parentheses, as shown in Figure 8. The rules for lettering height are discussed in Annex A.
Figure 8 — Enlarged features

ISO 128-3:2020(E)

For unambiguous relation between the circle and the identification letter, a leader line by a continuous
narrow line (type 01.1) and a reference line by a continuous narrow line (type 01.1) should be drawn.
See Figure 9.
Figure 9 — Enlarged features with leader line
5 Reference indication for views and enlarged features
5.1 General
On large-format mechanical technical drawings and technical drawings consisting of more than one
drawing sheet with an extensive amount of views and enlarged features, the readability should be
improved by information (reference indication) after the identification letter of the views.
The purpose is to find the views(standards.iteh.ai)
and the identification letters more easily on the technical drawing or
drawings.
ISO 128-3:2020
On construction drawings, designations for views and enlarged features can be complemented by
general reference to other drawings5df5790a32a0/iso-128-3-2020
containing the views/features.
5.2 Details of the reference indication

The reference indication after the identification letter on the views shall be in accordance with
ISO 15519-1.
Examples with explanation are shown in Figure 10 and Figure 11.
Figure 10 — Details of the reference indication with a single drawing

ISO 128-3:2020(E)

Figure 11 — Details of the reference indication with multiple drawings
5.3 Examples of indication

Examples of indication are given in Table 1.
Table 1 — Examples of indication
(standards.iteh.ai)Interpretation
Indication on technical drawing
ISO 128-3:2020
5df5790a32a0/iso-128-3-2020
View A is represented at technical drawing

coordinates C10 on the same sheet.
The identification letter and reference arrow on the

main view is represented at technical drawing
coordinates A3 on the same sheet.
Enlarged feature Z is represented at technical drawing

coordinates D5 on sheet 2.

ISO 128-3:2020(E)

Table 1 (continued)
Indication on technical drawing Interpretation
The indication of the enlarged feature Z is represented

at technical drawing coordinates B3 on sheet 1.
6 General information on cuts and sections
6.1 General
The general rules for the arrangement of views apply equally when drawing cuts and sections.
6.2 Indication of cuts and sections
6.2.1 Cutting plane
The position of the cutting plane(s) shall be indicated by means of a cutting line represented with a
dashed dotted wide line (type 10.2) according to ISO 128-2:—, Annex E and Annex G. A straight cutting
plane shall be drawn (see Figure 12).
If the cutting plane changes its direction, the cutting line should only be drawn at the ends of the cutting
plane, where the cutting plane changes direction (see Figure 13).
(standards.iteh.ai)
If necessary for its legibility, the cutting line may be connected with a long-dashed dotted narrow line
of the type 04.1 according to ISO 128-2:—,ISO Annex D or 04.1 according to ISO 128-2:—, Annex F).
128-3:2020
The direction of viewing for the relevant cut and section is indicated by the reference arrows as defined
5df5790a32a0/iso-128-3-2020
in Annex A.
The designated cut and section can be located irrespective of the view in which the cutting plane is taken.
Representation of areas on cuts and sections is covered in Clause 7.
6.2.2 Identification of the cutting plane
Each cut and section plane shall be given clear identification with twice the same capital letter, once at
each of the cut and section arrows. This identification should be positioned for reading from the bottom
of the technical drawing.
The 30° or 90° cut and section arrow is defined in A.4, as is the lettering height of the identification.
6.2.3 Identification of the cuts and sections
The identification of the referenced cuts and sections shall be placed immediately above the relevant
representation. (see Figure 12 and 13).

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INTERNATIONAL ISO

Technical product documentation

iTeh STANDARD PREVIEW

COPYRIGHT PROTECTED DOCUMENT

ii ﻿ © ISO 2020 – All rights reserved

© ISO 2020 – All rights reserved ﻿ iii

This first edition cancels and replaces the following documents:

iv ﻿ © ISO 2020 – All rights reserved

iTeh STANDARD PREVIEW

© ISO 2020 – All rights reserved ﻿ v

Technical product documentation (TPD) — General

3 Terms and definitions

1) Under preparation. Stage at the time of publication: ISO/FDIS 128-2:2020.

© ISO 2020 – All rights reserved ﻿ 1

[SOURCE: ISO 10209:2012, 3.11, modified — Note 1 to entry added.]

[SOURCE: ISO 10209:2012, 3.61, modified — Note 1 to entry added.]

2 ﻿ © ISO 2020 – All rights reserved

Figure 1 — Identification of referenced views

4.3 Partial views

© ISO 2020 – All rights reserved ﻿ 3

Figure 2 — Partial view

4.4 Simplified view of symmetrical parts

iTeh STANDARD PREVIEW

a) Example 1 b) Example 2 c) Example 3

Figure 3 — Examples of simplified views of symmetrical parts

4.5 First angle projection method

4.6 First angle projection method views

4 ﻿ © ISO 2020 – All rights reserved

— the view from the right, (d), is placed on the left;

Figure 4 — First angle projection method

iTeh STANDARD PREVIEW

Figure 5 — First angle projection graphical symbol

4.8 Third angle projection method

4.9 Third angle projection method views

© ISO 2020 – All rights reserved ﻿ 5

Figure 6 — Third angle projection method

4.10 Third angle projection graphical symbol

Figure 7 — Third angle projection graphical symbol

4.11 Other projection methods

4.12 Enlarged features

Figure 8 — Enlarged features

6 ﻿ © ISO 2020 – All rights reserved

Figure 9 — Enlarged features with leader line

5 Reference indication for views and enlarged features

5.2 Details of the reference indication

Figure 10 — Details of the reference indication with a single drawing

© ISO 2020 – All rights reserved ﻿ 7

Figure 11 — Details of the reference indication with multiple drawings

5.3 Examples of indication

View A is represented at technical drawing

The identification letter and reference arrow on the

Enlarged feature Z is represented at technical drawing

8 ﻿ © ISO 2020 – All rights reserved

The indication of the enlarged feature Z is represented

6 General information on cuts and sections

6.2 Indication of cuts and sections

6.2.1 Cutting plane

6.2.2 Identification of the cutting plane

6.2.3 Identification of the cuts and sections

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