INTERNATIONAL IS0

STANDARD 128-21
First edition
1997-03-01

Technical drawings - General principles

of presentation -
Part 21:
Preparation of lines by CAD systems

Dessins techniques - Principes gkkraux de reprbsentation -

Partie 2 I: Prkparation des traits par systBmes de CA0

This material is reproduced from IS0 documents under International

Organization for Standardization (ISO) Copyright License number
IHSllCC11996. Not for resale. No part of these IS0 documents may be
reproduced in any form, electronic retrieval system or otherwise, except as
allowed in the copyright law of the country of use, or with the prior written
consent of IS0 (Case postale 56,121l Geneva 20, Switzerland, Fax +41 22
734 IO 79) IHS or the IS0 Licenser’s members.

Reference number
IS0 128-21 :I 997(E)

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 IS0 128-21:1997(E)

Foreword

IS0 (the International Organization for Standardization) is a worldwide

federation of national standards bodies (IS0 member bodies). The work of
preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are

circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.

International Standard IS0 128-21 was prepared by Technical Committee

lSO/-rC 10, Technical drawings, product definition and related
documentation, Subcommittee SC 1, Basic conventions.

IS0 128 consists of the following parts, under the general title Technical
drawings - General principles of presentation:

- Part 20: Basic conventions for lines

- Part 27: Preparation of lines by CAD systems
- Part 23: Lines on construction drawings

Further parts of IS0 128 are planned, covering other general principles of
presentation including those for the application of lines within drawings of
various technical fields.

Annex A of this part of IS0 128 is for information only.

0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be
reproduced or utilized in any form or by any means, electronic or mechanical, including
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 CH-1211 Geneve 20 Switzerlandl l

Internet centralQiso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
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 @ IS0 IS0 128-21:1997(E)

Introduction

Today the appearance of non-continuous lines on technical drawings

prepared by computer-aided design (CAD) systems varies considerably
between different systems. For that reason the standardized rules
established by this International Standard, in addition to those in
IS0 128-20, are intended as an aid for the consistent appearance of line
elements calculated by computers and drawn by plotters.

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. ..
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 INTERNATIONAL STANDARD 0 IS0 IS0 128-21:1997(E)

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Technical drawings - General principles of presentation -

Part 21:
Preparation of lines by CAD systems

1 Scope

This part of IS0 128 specifies procedures for the calculation of the most important basic types of non-continuous
lines according to IS0 128-20 and their line elements.

2 Normative references

The following standards contain provisions which, through reference in this text, constitute provisions of this part
of IS0 128. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of IS0 128 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently
valid International Standards.

IS0 128-20:1996, Technical drawings - General principles of presentation - Part 20: Basic conventions for lines.

IS0 5455: 1979, Technical drawings - Scales.

3 Definitions

For the purposes of this part of IS0 128 the definitions given in IS0 128-20 apply.

4 Calculation of line elements

4.1 Line type No. 02 (dashed line)

See figure 1 for the configuration of this type of line.

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 IS0 128-21:1997(E) 0 IS0

(1): Line segment

Figure 1

EXAMPLE

See figure 2.

-- -----__-_ T
-- ’
T
I
- /

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Figure 2

Formulae:

a) Length of the line: 11 = lo

b) Number of line segments within the line: n= I1 Lid2d (rounded)

11- 3dn
cl Length of the dashes: 12 =-
n+l
d) Minimum length of this line: llmin = lomin = 27d
(2 dashes 12d, 1 gap 3d)

If dashed lines with a length less than 11 = 27d, have to be drawn, a larger scale from IS0 5455 shall be used (i.e.
the elements are drawn at a larger scale).

This line may be drawn with a constant length of dashes (12d). In this case one end of the line may be a shorter or
longer dash.

EXAMPLE

11 = 125 d = 0,35

n- 125-4.2,
=23,01=2J
5.25

125-2415
12 =
=4202

I
24

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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

4.2 Line type No. 04 (long dashed dotted line)

See figure 3 for the configuration of this type of line.

~~-.-.----.-.-.----+ '
A/
-0

(I 1: Line segment
Figure 3

EXAMPLE

See figure 4.

A
---I
I I
I I
I : I
--.-.--. .--.-.-.--
cp

12d

Figure 4

Formulae:

a) Length of the line: l1 = 10 + 24d

(line extended over the outlines at both sides)

b) Number of line segments within the line: n = “,‘,“d” (rounded)

I, - 6,5dn
c) Length of the long dashes: 13 =
n-t1

d) Minimum length of this line: 1lmin = 54,5d

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 IS0 128-21:1997(E) 0 IS0

Lines shorter than I1 = 54,5d shall be drawn as continuous narrow lines. In order to comply with the requirements
of IS0 128-20:1996, clause 5, the length of the long dashes of this line may be decreased or increased.

EXAMPLE

lo = 125 d = 0,25

1, =125+6=m

131-6
a=------=16,3932E
7,625

l = 131- 26,00
3 =6,176
17

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Interpretation of the result: A long dashed dotted line of length 131 mm and line width 0,25 mm, consists of 16 line
segments of length 7,801 mm (6,176 mm + 0,750 mm + 0,125 mm + 0,750 mm) and 1 long dash of length
6.176 mm.

4.3 Line type No. 05 (long dashed double-dotted line)

See figure 5 for the configuration of this type of line.

(1): Line segment

Figure 5

EXAMPLE

See figure 6.

t I
/

Figure 6

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 0 IS0 IS0 128-21:1997(E)

Formulae:

a) Length of the line: 11 =10-x

b) Number of line segments within the line: n= I1 i4y (rounded)

1, - IOdn
c) Length of the long dashes: I, =
n+l
d) Minimum length of this line: 1Imin = 58d

Lines shorter than 11 = 58d shall be drawn at a larger scale, in accordance with IS0 5455.

It is permissible to draw the long dashes with a change in direction, see figure 7.

\ .
I ‘\

Figure 7

In order to comply with the requirements of IS0 128-20: 1996, clause 5, the length of the long dashes of this line
may be increased or decreased.

EXAMPLE

lo= 128 d = 0,35 ;=1,5

I, =128-3=U

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125 - 64
n= = 9,798 Slo
1 1.9

~EJ-~~.OO=~~~~
I, =
I
11

4.4 Line type No. 07 (dotted line)

See figure 8 for the configuration of this type of line.

3d

AL--r
14

(1): Line segment

Figure 8

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 IS0 128-21:1997(E) 0 IS0

EXAMPLE

See figure 9.

Figure 9

Formulae:

a) Length of the line: 11 = Eo

b) Number of line segments within the line: n = I1 iif” (rounded)

1, - 3dn
c) Length of the dots: 14 =
n+l

d) Minimum length of this line: llmin = 7,5d

EXAMPLE

L1 = 125 d = 0,5

125 - 0.25
n= 1,75 = 71,286 e 71

L = ‘25-10615 =0257
4 I
72

4.5 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: 11 = lo

1, - 24d
b) Number of line segments within the line: n= (rounded)
32d

I, - 12dn
c) Length of the long dashes: 13 =
n+l
Lengths of the short dashes: 6d (see table 3 of IS0 128-20:1996)

d) Minimum length of this line: Llmin = 60d

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 0 IS0 IS0 128-21:1997(E)

EXAMPLE

11 = 125 d = 0,5

125-12
n= =7,0632’z
16

1 = 125-42
3 =I0375
r
8

4.6 Line type No. 09 (long dashed double-short dashed line)

The conditions for this line type are similar to those for type No. 05 and the formulae b), c) and d) are slightly
modified as follows:

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a) Length of the line: 11 =lo

b) Number of line segments within the line: n= I1 ildl (rounded)

I =I,-2ldn
c) Length of the long dashes: 3
n+l
Length of the short dashes: 6d (see table 3 of IS0 128-20:1996)

d) Minimum length of this line: 11min = 69d

EXAMPLE

II = 125 d = 0,25

125-6
II=-=10578gu
11.25 L

1 = 125-57,75
3 = 5,604
12

4.7 Examples of combinations of basic types of line

4.7.1 Two types of lines superimposed

See figure 10 for the configuration of this type of line.

a) b)

I -1

(1): Line segment

a): Continuous line No. 01: line width, e.g. 0,25 mm
b): Dashed spaced line No. 03: line width, e.g. 0,5 mm
Figure 10

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 IS0 128-21:1997(E)

EXAMPLE

See figure 11.

Figure 11

Formulae:

a) Length of the line: 11 = &j + 16

b) Number of line segments within the line: n = &-- (rounded)

2
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l1 - 18d-p
c) Length of the dashes: 12 =
n

d) Minimum length of this line: /lmin = 30d2

EXAMPLE

i1 = 125 dl = 0,25 d2 = 0,5

I J25-72
2
= 6,625
8

Interpretation of the result: This line consists of a continuous line 125 mm long and 0,25 mm wide as well as a
dashed spaced line of width 0,5 mm and 8 dashes of length 6,625 mm, spaced 9 mm apart (18d2, see table 3 of
IS0 128-20:1996). The ends are 45 mm in length (9d2).

4.72 Line with zigzags

See figure 12 for the configuration of this type of tine.

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 Q IS0 IS0 128-21:1997(E)

Figure 12

EXAMPLES

See figures 13 and 14.

Figure 13 Figure 14

Formulae:

a) Length of the line: l1 =lo+lOd

b) Number of zigzags within the line: II = -4 + 1 (rounded, 11< 40 makes n = I)

80

c) Length of the dashes between zigzags: 1, = !I- - 7,5d

n
d) Length of the dashes at the ends of the line:

- if two or more zigzags: l3 +

- 1, - 7,5d
if one zigzag: 13 =
2
If 10 G IOd, the zigzag shall be arranged as shown in figure 14.

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 IS0 128-21:1997(E)

EXAMPLE

lo = 125 d = 0,25

1, = 125 + 2,5 = 127,5

127,5
n=F+1=2,594cQ

1 = 1273
- - (7.5 x 0,25) = 40,625
2 3

1, = F = 20,313

Interpretation of the result: A line with zigzags of a length of 127,5 mm and a line width of 0,25 mm is drawn with 3
zigzags. The distance between the zigzags is 40,625 mm and the length of the dashes at the ends is 20,313 mm.

4.7.3 “Railway” line

See figure 15 for the configuration of this type of line.

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1, min.
t

(II

(1): Line segment

a): Continuous line No. 01
b): Dashed spaced line No. 03
Figure 15

EXAMPLE

See figure 16.

I------
-+ ---r-l- -- I- -L
:‘---j-
-I
I !
-- I -. L
t
*t cl:x: I
A A
I

Figure 16

IO
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 0 IS0 IS0 128-21:1997(E)

Formulae:

a) Length of the line: 17 = 10

1, -12d
b) Number of line segments within the line: n=
30d (rounded)
l J,-18dn
c) Length of the dashes: 2
n+l

d) Minimum length of this line: llmin = 42d

EXAMPLE
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I1 = 125 d = 0,35

125 - 42
n= = 11,505 212
10.5

1 = 125-75,60
2 -3800
12+1 -r

Interpretation of the results: A “railway” line of length 125 mm and line width 1,4 mm (4 x 0,35 mm) consists of 12
complete line segments of length 10,100 mm (3,800 mm + 6,300 mm) and one dash of length 3,800 mm.

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 IS0 128-21:1997(E) 0 IS0

Annex A
(informative)

Bibliography

[I 1 IS0 6428:1982, Technical drawings - Requirements for microcopying.

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 IS0 128-21:1997(E) 0 IS0

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ICS 01.100.01; 35.240.10

Descriptors: drawings, technical drawings, computer aided design, lines, presentation, dimensions, generalities.

Price based on 12 pages

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