EN ISO 128-2:2020

SLOVENSKI STANDARD
01-oktober-2020
Nadomešča:
SIST EN ISO 128-20:2002
SIST EN ISO 128-21:2002
Tehnična dokumentacija izdelkov - Splošna načela prikazovanja - 2. del: Osnovni
dogovori za črte (ISO 128-2:2020)
Technical product documentation - General principles of representation - Part 2: Basic
conventions for lines (ISO 128-2:2020)
Technische Produktdokumentation (TPD) - Allgemeine Grundlagen der Darstellung - Teil
2: Linien, Grundregeln (ISO 128-2:2020)
Documentation technique de produits - Principes généraux de représentation - Partie 2:
Conventions de base pour les traits (ISO 128-2:2020)
Ta slovenski standard je istoveten z: EN ISO 128-2:2020
ICS:
01.110 Tehnična dokumentacija za Technical product
izdelke documentation
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 128-2
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2020
EUROPÄISCHE NORM
ICS 01.100.01 Supersedes EN ISO 128-20:2001, EN ISO 128-21:2001
English Version
Technical product documentation - General principles of
representation - Part 2: Basic conventions for lines (ISO
128-2:2020)
Documentation technique de produits - Principes Technische Produktdokumentation (TPD) - Allgemeine
généraux de représentation - Partie 2: Conventions de Grundlagen der Darstellung - Teil 2: Linien,
base pour les traits (ISO 128-2:2020) Grundregeln (ISO 128-2:2020)
This European Standard was approved by CEN on 2 July 2020.

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, Turkey 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
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 128-2:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 128-2:2020) has been prepared by Technical Committee ISO/TC 10 "Technical
product documentation" in collaboration with Technical Committee CEN/SS F01 “Technical drawings”
the secretariat of which is held by CCMC.
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 February 2021, and conflicting national standards
shall be withdrawn at the latest by February 2021.
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 128-20:2001 and EN ISO 128-21:2001.
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, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 128-2:2020 has been approved by CEN as EN ISO 128-2:2020 without any modification.

INTERNATIONAL ISO
STANDARD 128-2
First edition
2020-07
Technical product documentation
(TPD) — General principles of
representation —
Part 2:
Basic conventions for lines
Documentation technique de produits (TPD) — Principes généraux de
représentation —
Partie 2: Conventions de base pour les traits
Reference number
ISO 128-2:2020(E)
©
ISO 2020
ISO 128-2:2020(E)
© ISO 2020
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 2020 – All rights reserved

ISO 128-2:2020(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Types of lines . 3
4.1 General . 3
4.2 Basic types . 3
4.3 Line sub types . 4
4.4 Variations of the basic types of lines . 4
4.5 Combinations of lines with the same length . 4
4.5.1 Arrangement of two or more lines parallel to each other . 4
4.5.2 Arrangement of two different types of lines . 5
4.5.3 Arrangement of two continuous lines parallel to each other with regularly
recurring connecting elements between them . 5
4.5.4 Arrangement of regularly recurring geometric pictorial elements in
association with continuous lines . 5
5 Line dimensions . 6
5.1 Line width . 6
5.2 Deviation in line width . 6
5.3 Configuration of lines . 6
6 Draughting of lines . 7
6.1 Spacing . 7
6.2 Junctions . 7
6.2.1 Types . 7
6.2.2 Representation . 9
6.3 Location of a second line .10
6.4 Hierarchy of overlapping lines .10
7 Colours .11
8 Designation .11
9 Basic conventions and applications for leader lines and reference lines .11
9.1 Presentation of leader lines .11
9.2 Representation of reference lines .14
9.3 Indication of instructions.15
Annex A (informative) Preparation of lines by CAD systems .17
Annex B (normative) Lines on construction technical drawings .30
Annex C (informative) Examples of application on construction technical drawings .33
Annex D (normative) Types of lines and their application on mechanical engineering
technical drawings .39
Annex E (informative) Examples of application on mechanical engineering technical drawings.43
Annex F (normative) Types of lines and their application on shipbuilding technical drawings .56
Annex G (informative) Application examples of the different types of lines on shipbuilding
technical drawings .58
Bibliography .69
ISO 128-2:2020(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.
This document was prepared by Technical Committee ISO/TC 10, Technical product documentation.
This first edition cancels and replaces the following documents:
— ISO 128-20:1996
— ISO 128-21:1997
— ISO 128-22:1999
— ISO 128-23:1999
— ISO 128-24:2014
— ISO 128-25:1999
The main changes to these documents are as follows:
— harmonization of the former parts listed above;
— introduction of the hierarchy of overlapping lines.
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 128-2:2020(E)
Introduction
ISO 128-2 contains generally applicable rules for the presentation of lines in all kinds of technical
product documentation.
All figures in this document have been drawn in first-angle projection. 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 lines within drawings of special technical fields varies considerably. Therefore, rules
of application specific to technical fields are given in Annexes B to G.
Annex A provides information for the calculation of the most important basic types of non-continuous
lines according to types of lines and their line elements.
INTERNATIONAL STANDARD ISO 128-2:2020(E)
Technical product documentation (TPD) — General
principles of representation —
Part 2:
Basic conventions for lines
1 Scope
This document establishes the types of lines used in technical drawings (e.g. diagrams, plans or
maps), their designations and their configurations, as well as general rules for the draughting of lines.
In addition, this document specifies general rules for the representation of leader and reference lines
and their components as well as for the arrangement of instructions on or at leader lines in technical
documents. Annexes have been provided for specific information on mechanical, construction and
shipbuilding technical drawings.
For the purposes of this document the term “technical drawing” is interpreted in the broadest
possible sense encompassing the total package of documentation specifying the product (workpiece,
subassembly, assembly).
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 128-3, Technical drawings — General principles of representation — Part 3: Views, sections and cuts
ISO 128-15, Technical product documentation (TPD) — General principles of presentation — Part 15:
Presentation of shipbuilding drawings
ISO 129-1, Technical product documentation (TPD) — Presentation of dimensions and tolerances — Part 1:
General principles
ISO 129-5, Technical product documentation (TPD) — Presentation of dimensions and tolerances — Part 5:
Dimensioning of structural metal work
ISO 1101, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,
orientation, location and run-out
ISO 2203, Technical drawings — Conventional representation of gears
ISO 2538-2, Geometrical product specifications (GPS) — Wedges — Part 2: Dimensioning and tolerancing
ISO 2553, Welding and allied processes — Symbolic representation on drawings — Welded joints
ISO 3040, Geometrical product specifications (GPS) — Dimensioning and tolerancing — Cones
ISO 3766, Construction drawings — Simplified representation of concrete reinforcement
ISO 4463-1, Measurement methods for building — Setting-out and measurement — Part 1: Planning and
organization, measuring procedures, acceptance criteria
ISO 4463-3, Measurement methods for building — Setting-out and measurement — Part 3: Check-lists for
the procurement of surveys and measurement services
ISO 128-2:2020(E)
ISO 5261, Technical drawings — Simplified representation of bars and profile sections
ISO 5455, Technical drawings — Scales
ISO 5456-4, Technical drawings — Projection methods — Part 4: Central projection
ISO 5459, Geometrical product specifications (GPS) — Geometrical tolerancing — Datums and datum systems
ISO 6410-1, Technical drawings — Screw threads and threaded parts — Part 1: General conventions
ISO 6428, Technical drawings — Requirements for microcopying
ISO 7437, Technical drawings — Technical drawings — Construction drawings — General rules for
execution of production drawings for prefabricated structural components
ISO 7519, Technical drawings — Construction drawings — General principles of presentation for general
arrangement and assembly drawings
ISO 8560, Technical drawings — Construction drawings — Representation of modular sizes, lines and grids
ISO 10110-1, Optics and photonics — Preparation of drawings for optical elements and systems —
Part 1: General
ISO 10135, Geometrical product specifications (GPS) — Drawing indications for moulded parts in technical
product documentation (TPD)
ISO 10209, Technical product documentation — Vocabulary — Terms relating to technical drawings,
product definition and related documentation
ISO 11091, Construction drawings — Landscape drawing practice
ISO 12671, Thermal spraying — Thermally sprayed coatings — Symbolic representation on drawings
ISO 15785, Technical drawings — Symbolic presentation and indication of adhesive, fold and pressed joints
ISO 15787, Technical product documentation — Heat-treated ferrous parts — Presentation and indications
ISO 16792, Technical product documentation — Digital product definition data practices
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:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
graphical basic element
continuous graphical object with rounded or squared end shape which is represented in any way (e.g.
straight, curved), which has a length and a width
Note 1 to entry: See Figure A.1.
3.2
dot
graphical basic element (3.1) having a length equal to the width, d
Note 1 to entry: See Figure A.2.
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ISO 128-2:2020(E)
3.3
line
set of one or more graphical basic elements (3.1) having a length of more than the width
Note 1 to entry: See Figure A.3.
3.4
technical drawing
drawing showing a technical installation, process or product with a view to clarifying its structure and
enabling its construction
[SOURCE: ISO 5127:2017, 3.4.7.54, modified — Note 1 to entry removed.]
4 Types of lines
4.1 General
The line type designation consists of a combination of a basic line type and a subtype, depending on the
line width, see 4.2.
For the purposes of this document a line type application number is used to number the application
examples for the line types.
For applying line types to construction technical drawings Annex B shall be applied. For applying line
types to mechanical engineering technical drawings Annex D shall be applied. For applying line types
to ship building technical drawings Annex F shall be applied.
4.2 Basic types
The basic line types are given in Table 1.
Table 1 — Basic line types
No. Representation Description
01 Continuous line
02 Dashed line
03 Dashed spaced line
04 Long-dashed dotted line
05 Long-dashed double-dotted line
06 Long-dashed triplicate-dotted line
07 Dotted line
08 Long-dashed short-dashed line
ISO 128-2:2020(E)
Table 1 (continued)
No. Representation Description
Long-dashed double-short-dashed
line
10 Dashed dotted line
11 Double-dashed dotted line
12 Dashed double-dotted line
13 Double-dashed double-dotted line
14 Dashed triplicate-dotted line
15 Double-dashed triplicate-dotted line
4.3 Line sub types
The line sub types are given in Table 2.
Table 2 — Line sub types
Sub-type
Representation Description
a
no.
.1 Narrow
.2 Wide
.3 Extra wide
a
Line identification structure
4.4 Variations of the basic types of lines
The straight lines in Table 1 and the line widths of Table 2 can have variations as shown in Table 3.
Table 3 — Line variations
Representation Description
Uniform wavy continuous line
Uniform spiral continuous line
Uniform zigzag continuous line
Freehand / freeform curve continu-
ous line
NOTE  Table 3 contains only variations of the basic type of line No. 01. Variations of the basic types of Nos. 02 to 15 are
possible and are presented in the same way.
4.5 Combinations of lines with the same length
4.5.1 Arrangement of two or more lines parallel to each other
For examples see Figure 1.
4 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Figure 1 — Example of lines parallel to each other
4.5.2 Arrangement of two different types of lines
a) With different line widths superimposed. See Figure 2 a) and b) for examples.
a) A continuous line and a dotted line b) A continuous line and a dashed spaced line
Figure 2 — Example of superimposed lines
b) Arranged next to each other. See Figure 3 for an example.
Figure 3 — Two continuous narrow lines either side of a wide dashed line
4.5.3 Arrangement of two continuous lines parallel to each other with regularly recurring
connecting elements between them
See Figure 4 a) and b) for examples.
a) Filled circular elements b) Filled trapezoidal elements
Figure 4 — Example of lines parallel to each other with regularly recurring connecting
elements
4.5.4 Arrangement of regularly recurring geometric pictorial elements in association with
continuous lines
a) Without interruption of a continuous line. See Figure 5 for examples.
Figure 5 — Without interruption of a continuous line
b) With interruption of a continuous line. See Figure 6 for examples.
ISO 128-2:2020(E)
Figure 6 — With interruption of a continuous line
5 Line dimensions
5.1 Line width
The width, d, of all types of lines shall be one of the following depending on the type and size of the
technical drawing. This series is based on a common ratio 1: √2 (≈1:1,4).
0,13 mm; 0,18 mm; 0,25 mm; 0,35 mm; 0,5 mm; 0,7 mm; 1 mm; 1,4 mm; 2 mm.
The widths of extra wide, wide and narrow lines are in the ratio 4:2:1.
The line width of any one line shall be constant throughout the whole line.
See Annexes B, D and F for information on line widths pertaining to construction, mechanical and
shipbuilding technical drawings.
5.2 Deviation in line width
Line widths can deviate from those specified in 5.1 providing that it is possible to differentiate
unambiguously between two adjacent lines with different widths. If technical drawing equipment
which produces constant line width is used, the deviation in line width between two such lines shall not
be greater than ± 0,1d.
5.3 Configuration of lines
For the preparation of technical drawings, the lengths of line elements should conform to those of
Table 4.
Table 4 — Lengths of line elements
Drawing element Line type no. Length
04 to 07 and
Dot ≤ d
10 to 15
02 and
Gap 3d
04 to 15
Short dash 08 and 09 6d
02, 03 and
Dash 12d
10 to 15
04 to 06,
Long dash ≈24d
08 and 09
Space 03 18d
NOTE  The lengths shown in this table are valid for line elements with semi-circular and
squared ends. In the case of line elements with semi-circular ends, the length of the line
element corresponds to the distance covered by a technical pen (with a tubular tip and
using India ink) from the origin up to the end of the line element. The total length of such
a line element is the sum of the length shown in this table, plus d.
6 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Formulae for the calculation of some of the basic types of lines and line elements are given in Annex A.
The formulae are intended to facilitate the preparation of technical drawings using computer-aided
design (CAD) systems.
6 Draughting of lines
6.1 Spacing
The minimum space between parallel lines should not be less than 0,7 mm.
In certain cases when computer-aided technical drawing techniques are used, the spacing of lines on
the technical drawing does not represent the actual spacing, for example for the representation of
screw threads. This has to be considered when data sets are established, for example for the operation
of machine tools.
6.2 Junctions
6.2.1 Types
The basic types of lines, nos. 02 to 06 and nos. 08 to 15, should meet at a dash to avoid ambiguity; see
Figures 7 to 12.
Figure 7 — Long-dashed short-dashed lines intersecting as a cross
Figure 8 — Dashed lines intersecting as a cross
ISO 128-2:2020(E)
Figure 9 — Dashed lines intersecting as a partial cross
Figure 10 — Four dashed lines meeting at an intersection
Figure 11 — Dash dotted lines intersecting as a cross and dashed lines meeting at corners
Figure 12 — Dashed lines meeting at corners and at intersection
Lines of basic type no. 07 should meet at a dot to avoid ambiguity, see Figure 13.
8 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Figure 13 — Dotted lines intersecting at a dot
6.2.2 Representation
Techniques for applying the recommendations of 6.2.1 are to start the lines at the junction (see
Figure 14) or by using a complete, or partial, cross or Y (see Figures 15 and 16).
Figure 14 — Partial cross intersection
ISO 128-2:2020(E)
Figure 15 — Cross intersection
Figure 16 — Y intersection
6.3 Location of a second line
Two different ways of presenting two parallel lines are shown in Figures 17 and 18.
Figure 17 — Example of parallel lines with solid line above dashed line
Figure 18 — Example of parallel lines with dashed line above solid line
6.4 Hierarchy of overlapping lines
The rules of overlapping types of lines are defined in Annex D.
10 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
7 Colours
Lines shall be drawn in black or white depending on the colour of the background. By default, lines
are black on a white background. Other standardized colours may also be used for technical drawing
standardized lines. In this case, the meaning of the colours shall be explained.
8 Designation
The designation of the basic types of lines shall comprise the following elements in the order given,
with spaces between the elements:
a) “Line”;
b) reference to this document;
c) dash separator;
d) the number of the basic type in accordance with Table 1;
e) the multiplication sign “×”;
f) the line width in accordance with 5.1;
g) forward slash (when the colour is indicated);
h) colour (when indicated).
EXAMPLES
Designation of a line of type no. 03 (03), line width 0,25 mm (0,25):
Line ISO 128-2 - 03 × 0,25
Designation of a line of type no. 05 (05), line width 0,13 mm (0,13) and blue in colour:
Line ISO 128-2 - 05 × 0,13/blue
9 Basic conventions and applications for leader lines and reference lines
9.1 Presentation of leader lines
Leader lines are executed as continuous narrow lines (type 01.1) in accordance with this document.
They are drawn at an angle to the relevant representation and/or the frame limiting the drawing sheet,
and not parallel to nearby lines, such as hatching lines. The inclination to the relevant lines shall be >15°.
See Figures 19 to 31.
Leader lines may be drawn with sharp kinks (see Figure 23), and two or more leader lines may
start from the same point (see Figures 20, 23, 25, 26 and 29). They should not cross other leader
lines (see Figure 23) except when the leader line starts from the same point and is colinear (see
Figure 25, 26 and 29), reference lines or indications, such as graphical symbols or dimensional values.
Leader lines shall terminate at the end which touches the features as follows:
— with a closed and filled arrowhead or a closed arrowhead as per ISO 129-1 if the leader line ends
at lines which represent outlines or edges of parts, piping or cables in plans, charts or diagrams;
arrowheads are also drawn at crossing points of these lines with other lines, for example lines of
symmetry (see the examples given in Figures 19 to 25);
ISO 128-2:2020(E)
If several parallel lines have to be designated, oblique strokes instead of arrowheads are permitted (see
IEC 61082-1). See the example given in Figure 26.
— with a dot (d = 5 × line width) if the leader line ends on the surface of an object (see the examples
given in Figures 27 to 29);
— without any termination if the leader line ends at another line, for example dimension line or line of
symmetry (see the examples given in Figures 30 and 31).
Figure 19 — Example of a leader line terminating at the edge of a diameter
Figure 20 — Example of leader lines starting at the same point and terminating at part edges
Figure 21 — Example of leader lines terminating at outlines
Figure 22 — Example of leader lines not overlapping cross section lines
Figure 23 — Example of a leader line with a sharp kink
Figure 24 — Example of a leader line terminating a the crossing point of two lines
12 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Figure 25 — Example of colinear leader lines starting from the same point and terminating
with arrows
Figure 26 — Example of a colinear leader lines starting from the same point and terminating
with oblique strokes
Figure 27 — Example of a leader line terminating with a dot to a surface area
Figure 28 — Example of a leader line terminating with a dot to a surface
Figure 29 — Example of colinear leader lines starting from the same point and terminating
with dots
Figure 30 — Example of a leader line ending at a dimension line without any termination mark
Figure 31 — Example of a leader line without any termination mark
ISO 128-2:2020(E)
9.2 Representation of reference lines
Reference lines are continuous narrow lines (type 01.1) in accordance with Clause 4. A reference line
can be added to each leader line or dimension line. It is drawn in one of the reading directions of the
technical drawing.
The reference line shall be drawn:
— either with a fixed length, i.e. 20 × line width of the reference line (see the examples given in
Figures 33 and 34; or
— with a length adapted to the length of the indicated instructions (see the examples given in
Figures 32, 35, 39 and 40).
Figure 32 — Example of a reference line adapted to the thread callout length
Figure 33 — Example of a reference line with a fixed length for a surface finish
Figure 34 — Example of a reference line with a fixed length for a dimension
Figure 35 — Example of a reference line adapted to the thread callout length
In particular cases of application, the reference line has to be drawn (see the example given in Figure 33).
However, the reference line can be omitted if the leader line is drawn in one of the reading directions of
the technical drawing, if the indicated instructions are written in the same direction (see the example
given in Figure 36), and in all other cases in which this line is not applicable (see the examples given in
Figures 30, 37 and 38).
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ISO 128-2:2020(E)
Figure 36 — Example of a reference line for dimension being omitted
Figure 37 — Example of a reference line for a surface finish being omitted
Figure 38 — Example of an omitted reference line
9.3 Indication of instructions
The instructions belonging to the leader lines, dimension lines and reference lines shall be indicated as
follows:
— above the reference line (see the example given in Figures 32, 35, 39 and 40 and in Annex E);
— centrically at the end of the leader, dimension, or reference line (see the example given in
Figure 34 and 36) in one of the reading directions of the drawing; or
— within graphical symbols according to the valid international standards (see the examples given in
Annex E).
Taking into account legibility, the requirements in ISO 6428 shall be followed and the instructions shall
be written at a distance of twice the line width of the reference line above the reference line. They shall
not be drawn within the reference line and they shall not touch it.
Figure 39 — Example of instructions above a reference line
If individual layers or assembled parts of an object are designated with one leader line, the order of
the indications shall correspond with the order of the layers or the parts (see the example given in
Figure 40).
ISO 128-2:2020(E)
Figure 40 — Example of assembled parts of an object designated with one leader line
16 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Annex A
(informative)
Preparation of lines by CAD systems
A.1 Calculation of line elements
This annex specifies procedures for the calculation of the most important basic types of non-continuous
line types and their line elements.
A.2 Graphical basic element
See Figure A.1 for an example of a configuration of a graphical basic element.
Figure A.1 — Configuration of a graphical basic element
A.3 Dot
See Figure A.2 for the configuration of a dot.
Figure A.2 — Configuration of a dot
A.4 Line
See Figure A.3 for the configuration of a line.
Figure A.3 — Configuration of a line
ISO 128-2:2020(E)
A.5 Line type no. 02 (dashed line)
See Figure A.4 for the configuration of this type of line.
Figure A.4 — Configuration of line type no. 02 (dashed line)
EXAMPLE See Figure A.5.
Figure A.5 — Example of line type no. 02 (dashed line)
Formulae:
a) Length of the line: ll=
b) Number of line segments within the line: ld−12
n=
15d
c) Length of the dashes:
ld−3 n
l =
n+1
d) Minimum length of this line: ll==27d
1min 0min
If dashed lines with a length less than l = 27d have to be drawn, a larger scale from ISO 5455 shall be
used (i.e. the elements are drawn at a larger scale).
This line can be drawn with a constant length of dashes (12d). In this case one end of the line may be a
shorter or longer dash.
Number of line segments shall be rounded to an integer.
EXAMPLE
l = 125 d = 0,35
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ISO 128-2:2020(E)
125−42,
n= =23,0123
52, 5
125−24,15
l = =4,202
Interpretation of the result: A dashed line of length 125 mm and line width 0,35 mm consists of 23 line segments
of length 5,252 mm (4,202 mm + 1,050 mm) and one dash of length 4,202 mm.
A.6 Line type no. 04 (long-dashed dotted line)
See Figure A.6 for the configuration of this type of line.
Figure A.6 — Configuration of line type no. 04 (long-dashed dotted line)
EXAMPLE See Figure A.7.
Figure A.7 — Example of line type no. 04 (long-dashed dotted line)
Formulae:
a) Length of the line: ll=+24d
(line extended over the outlines at both sides)
b) Number of line segments within the line: ld−24
n=
30,5d
c) Length of the long dashes: ld−65, n
l =
n+1
d) Minimum length of this line: l = 54,5d
1min
ISO 128-2:2020(E)
Lines shorter than l = 54,5d shall be drawn as continuous lines. In order to conform with the
requirements of Clause 6, the length of the long dashes of this line may be decreased or increased.
Number of line segments shall be rounded to an integer.
EXAMPLE
l = 125 d = 0,25
l = 125 + 6 =131
131−6
n= =16,39316
7,625
131−26,00
l = =6,176
Interpretation of the result: a long-dashed dotted line of length 131 mm and line width 0,25 mm consists
of sixteen line segments of length 7,801 mm (6,176 mm + 0,750 mm + 0,125 mm + 0,750 mm) and one
long dash of length 6,176 mm.
A.7 Line type no. 05 (long-dashed double-dotted line)
See Figure A.8 for the configuration of this type of line.
Figure A.8 — Configuration of line type no. 05 (long-dashed double-dotted line)
EXAMPLE See Figure A.9.
Figure A.9 — Example of line type no. 05 (long-dashed double-dotted line)
20 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
Formulae:
a) Length of the line: ll≈−x
b) Number of line segments within the line:
ld−24
n=
34d
c) Length of the long dashes: ld−10 n
l =
n+1
d) Minimum length of this line: l = 58d
1min
Lines shorter than l = 58d shall be drawn at a larger scale, in accordance with ISO 5455.
It is permissible to draw the long dashes with a change in direction, see Figure A.10.
Number of line segments shall be rounded to an integer.
Figure A.10 — Long-dashed double-dotted line with a change in direction
In order to conform with the requirements of Clause 6, the length of the long dashes of this line may be
increased or decreased.
EXAMPLE
x
l = 128 d = 0,35 = 1,5
l = 128 – 3 =125
125−84,
n= =9,79810
11,9
125−35
l = =8,182
A.8 Line type no. 07 (dotted line)
See Figure A.11 for the configuration of this type of line.
ISO 128-2:2020(E)
Figure A.11 — Configuration of line type no. 07 (dotted line)
EXAMPLE See Figure A.12.
Figure A.12 — Example of line type no. 07 (dotted line)
Formulae:
a) Length of the line: ll=
b) Number of line segments within the line: ld−
n=
25, d
c) Length of the dots:
ld−15, n
l =
n+1
d) Minimum length of this line: l = 9d
1min
Number of line segments shall be rounded to an integer.
EXAMPLE
l = 125 d = 1
125−1
n= =49,65 0
25,
125−75
l = =09, 8
22 © ISO 2020 – All rights reserved

ISO 128-2:2020(E)
A.9 Line type no. 08 (long-dashed short-dashed line)
See Figure A.13 for the configuration of this type of line.
Figure A.13 — Configuration of line type no. 08 (long-dashed short-dashed line)
The conditions for this line type are the same as those for type no. 04 but the formulae are slightly
modified as follows:
a) Length of the line: ll=
b) Number of line segments within the line: ld−24
n=
32d
c) Length of the long dashes:
ld−12 n
l =
n+1
d) Lengths of the short dashes: 6d
e) Minimum length of this line: l = 60d
1min
Number of line segments shall be rounded to an integer.
EXAMPLE
l = 125 d = 0,5
125−12
n= =7,0637
125−42
l = =10,375
A.10 Line type no. 09 (long-dashed double-short-dashed line)
See Figure A.14 for the configuration of this type of line.
Figure A.14 — Configuration of line type no. 09 (long-dashed double-short-dashed line)
ISO 128-2:2020(E)
The conditions for this line type are simi
...