Synchronous belt drives — Vocabulary

ISO 5288:2017 specifies the terms and definitions related to the use of synchronous belt drives for mechanical power transmission and where positive indexing or synchronization is required.

Transmissions synchrones par courroies — Vocabulaire

ISO 5288:2017 spécifie les termes et définitions relatifs à l'utilisation des transmissions synchrones par courroies pour la transmission mécanique de puissance et lorsque l'indexation ou la synchronisation positive sont requises.

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5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
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03-Sep-2024
Completion Date
03-Sep-2024
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FINAL DRAFT
International
Standard
ISO/TC 41/SC 4
Synchronous belt drives —
Secretariat: ANSI
Vocabulary
Voting begins on:
Transmissions synchrones par courroies — Vocabulaire 2024-09-03
Voting terminates on:
2024-10-29
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 41/SC 4
Synchronous belt drives —
Secretariat: ANSI
Vocabulary
Voting begins on:
Transmissions synchrones par courroies — Vocabulaire
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2024
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General .1
3.2 Synchronous belts .2
3.2.1 General .2
3.2.2 Tooth profile .4
3.2.3 Type of belt drive .5
3.2.4 Structure .5
3.2.5 Teeth .6
3.3 Pulleys .9
3.3.1 General .9
3.3.2 Grooves . 13
3.3.3 Groove-generating tools .17
4 Symbols .21
Alphabetical index .23

iii
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
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 41, Pulleys and belts (including veebelts),
Subcommittee SC 4, Synchronous belt drives.
This fourth edition cancels and replaces the third edition (ISO 5288:2017), of which it constitutes a minor
revision. The change is as follows:
— Inclusion of Clause 4.
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
FINAL DRAFT International Standard ISO/FDIS 5288:2024(en)
Synchronous belt drives — Vocabulary
1 Scope
This document specifies the terms and definitions related to the use of synchronous belt drives for
mechanical power transmission and where positive indexing or synchronization is required.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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 General
3.1.1
synchronous belt drive
system composed of a synchronous belt (3.2.1.1) and at least one synchronous pulley (3.3.1.1)
Note 1 to entry: Synchronized motion and/or power is transmitted through the engagement of teeth on the belt with
grooves (3.3.2.1) on the pulleys.
Note 2 to entry: This belt drive has been known in the past by various names such as “timing belt drive”, “positive belt
drive” or “gear belt drive”.
3.1.2
centre distance
C
shortest distance between the axes of two synchronous pulleys (3.3.1.1) when the belt is under the prescribed
measuring force
Note 1 to entry: See Figure 1.
Figure 1
3.1.3
endless synchronous belt drive
synchronous belt drive (3.1.1) with applied endless synchronous belt
Note 1 to entry: See Figure 2.
Figure 2
3.1.4
open synchronous belt drive
synchronous belt drive (3.1.1) with applied open synchronous belt
Note 1 to entry: See Figure 3.
Figure 3
3.2 Synchronous belts
3.2.1 General
3.2.1.1
synchronous belt
belt with transverse teeth of rectangular or curvilinear cross-section extending from the base at regularly
spaced intervals
Note 1 to entry: Consult synchronous belt dimensional standards for the full details of belt profiles.
3.2.1.2
tooth pitch
P
b
linear distance between the axes of two consecutive teeth in a section of belt loaded to the prescribed
measuring force
Note 1 to entry: See Figure 4.

Figure 4
3.2.1.3
pitch line
circumferential line in the belt which keeps the same length when the belt is bent perpendicularly to its base
Note 1 to entry: See Figure 5.
Figure 5
3.2.1.4
pitch line differential
a
radial distance between the pitch line (3.2.1.3) and the root line (3.2.5.3)
Note 1 to entry: See Figure 6.
Figure 6
3.2.1.5
belt pitch length
L
p
length of the pitch line (3.2.1.3) of a belt
3.2.1.6
width
b
s
transverse dimension of the back of the belt
Note 1 to entry: See Figure 7.
Figure 7
3.2.1.7
height
h /h
s d
total height of a single-sided or double-sided belt
Note 1 to entry: See Figure 8.
a) Single-sided belt
b) Double-sided belt
Figure 8
3.2.2 Tooth profile
3.2.2.1
trapezoidal profile
transverse tooth (3.2.5.1) profile formed by a tooth flank (3.2.5.5) and tip with only straight lines
Note 1 to entry: See Figure 9.
Figure 9
3.2.2.2
curvilinear profile
transverse tooth (3.2.5.1) profile formed by a tooth flank (3.2.5.5) or tip that contains curved lines
Note 1 to entry: See Figure 10.
Figure 10
3.2.3 Type of belt drive
3.2.3.1
endless synchronous belt
closed synchronous belt (3.2.1.1)
Note 1 to entry: See Figure 11.
Figure 11
3.2.3.2
open synchronous belt
synchronous belt (3.2.1.1) with two ends
Note 1 to entry: See Figure 12.
Figure 12
3.2.4 Structure
3.2.4.1
single-sided synchronous belt
synchronous belt (3.2.1.1) with teeth located inside of the pitch line (3.2.1.3) at regularly spaced intervals
Note 1 to entry: See Figure 13.
Figure 13
3.2.4.2
double-sided synchronous belt
synchronous belt (3.2.1.1) with teeth located on both sides of the pitch line (3.2.1.3) at regularly spaced
intervals
Note 1 to entry: See Figure 14.

a) Staggered double-sided synchronous belt
b) Symmetrical double-sided synchronous belt
Figure 14
3.2.5 Teeth
3.2.5.1
tooth
generally transverse element protruding from the root of the belt which have the profile necessary to mesh
with the grooves (3.3.2.1) in a synchronous pulley (3.3.1.1)
Note 1 to entry: See Figure 15.
Figure 15
3.2.5.2
tip line
line joining the tips of the belt teeth
Note 1 to entry: See Figure 16.
Figure 16
3.2.5.3
root line
line joining the roots between the belt teeth
Note 1 to entry: See Figure 17.
Figure 17
3.2.5.4
tooth height
h
t
distance between the tip line (3.2.5.2) and the root line (3.2.5.3)
Note 1 to entry: See Figure 18.
Figure 18
3.2.5.5
flank
area defined by the width (3.2.1.6) of the belt tooth (3.2.5.1) and the portion of the tooth section contained
between the tooth tip radius and the tooth root radius or, if there is no tooth tip radius, contained between
the tip line (3.2.5.2) and the tooth root radius
Note 1 to entry: See Figure 19.
a)
b)
Figure 19
3.2.5.6
working flank
flank (3.2.5.5) of a belt tooth (3.2.5.1) in contact with the pulley groove flank when it is
transmitting power
Note 1 to entry: See Figure 20.

Figure 20
3.2.5.7
non-working flank
flank (3.2.5.5) of the tooth (3.2.5.1) opposite the working flank (3.2.5.6)
Note 1 to entry: See Figure 21.
Figure 21
3.2.5.8
radius at tooth tip
r
a
radius of a generally curved section of a belt tooth (3.2.5.1) that connects the
...


ISO/TC 41/SC 4
Secretariat: ANSI
Date: 2024-08-20
Synchronous belt drives — Vocabulary
Transmissions synchrones par courroies — Vocabulaire
FDIS stage
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
E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents
Foreword . iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 General . 1
3.2 Synchronous belts . 3
3.3 Pulleys . 14
4 Symbols . 33
Alphabetical index . 35

iii
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 documentsdocument 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).
Field Code Changed
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
document may beinvolve the subjectuse 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
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. 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 ).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation onof 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.htmlthe following URL: .
This document was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts)),
Subcommittee SC 4, Synchronous belt drives.
This thirdfourth edition cancels and replaces the secondthird edition (ISO 5288:2001),2017), of which has
been technically revised.it constitutes a minor revision. The main change is as follows:
— Inclusion of Clause 4compared.
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.htmlprevious edition is the inclusion
of include terms related to curvilinear synchronous belts.

iv
Synchronous belt drives — Vocabulary
1 Scope
This document specifies the terms and definitions related to the use of synchronous belt drives for mechanical
power transmission and where positive indexing or synchronization is required.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminologicalterminology 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 3.1 General
3.1.1
synchronous belt drive
system composed of a synchronous belt (3.2.1.1(3.2.1.1)) and at least one synchronous pulley (3.3.1.1(3.3.1.1))
Note 1 to entry: Synchronized motion and/or power is transmitted through the engagement of teeth on the belt with
grooves (3.3.2.1(3.3.2.1)) on the pulleys.
Note 2 to entry: This belt drive has been known in the past by various names such as “timing belt drive”, “positive belt
drive” or “gear belt drive”.
3.1.2
centre distance
C
shortest distance between the axes of two synchronous pulleys (3.3.1.1(3.3.1.1)) when the belt is under the
prescribed measuring force
Note 1 to entry: See Figure 1Figure 1.
Figure 1
3.1.3
endless synchronous belt drive
synchronous belt drive (3.1.1(3.1.1)) with applied endless synchronous belt
Note 1 to entry: See Figure 2Figure 2.

Figure 2
3.1.4
open synchronous belt drive
synchronous belt drive (3.1.1(3.1.1)) with applied open synchronous belt
Note 1 to entry: See Figure 3Figure 3.
Figure 3
3.2 3.2 Synchronous belts
3.2.1 3.2.1 General
3.2.1.1
synchronous belt
belt with transverse teeth of rectangular or curvilinear cross-section extending from the base at regularly
spaced intervals
Note 1 to entry: Consult synchronous belt dimensional standards for the full details of belt profiles.
3.2.1.2
tooth pitch
P
b
linear distance between the axes of two consecutive teeth in a section of belt loaded to the prescribed
measuring force
Note 1 to entry: See Figure 4Figure 4.
Figure 4
3.2.1.3
pitch line
circumferential line in the belt which keeps the same length when the belt is bent perpendicularly to its base
Note 1 to entry: See Figure 5Figure 5.

Figure 5
3.2.1.4
pitch line differential
a
radial distance between the pitch line (3.2.1.3(3.2.1.3)) and the root line (3.2.5.3(3.2.5.3))
Note 1 to entry: See Figure 6Figure 6.

Figure 6
3.2.1.5
belt pitch length
L
p
length of the pitch line (3.2.1.3(3.2.1.3)) of a belt
3.2.1.6
width
b
s
transverse dimension of the back of the belt
Note 1 to entry: See Figure 7Figure 7.

Figure 7
3.2.1.7
height
h /h
s d
total height of a single-sided or double-sided belt
Note 1 to entry: See Figure 8Figure 8.

a) Single-sided belt
b) Double-sided belt
a) Single-sided belt
b) Double-sided belt
Figure 8
3.2.2 3.2.2 Tooth profile
3.2.2.1
trapezoidal profile
transverse tooth (3.2.5.1(3.2.5.1)) profile formed by a tooth flank (3.2.5.5) and tip with only straight lines
Note 1 to entry: See Figure 9Figure 9.

Figure 9
3.2.2.2
curvilinear profile
transverse tooth (3.2.5.1(3.2.5.1)) profile formed by a tooth flank (3.2.5.5) or tip that contains curved lines
Note 1 to entry: See Figure 10Figure 10.

Figure 10
3.2.3 3.2.3 Type of belt drive
3.2.3.1
endless synchronous belt
closed synchronous belt (3.2.1.1(3.2.1.1))
Note 1 to entry: See Figure 11Figure 11.

Figure 11
3.2.3.2
open synchronous belt
synchronous belt (3.2.1.1(3.2.1.1)) with two ends
Note 1 to entry: See Figure 12Figure 12.

Figure 12
3.2.4 3.2.4 Structure
3.2.4.1
single-sided synchronous belt
synchronous belt (3.2.1.1(3.2.1.1)) with teeth located inside of the pitch line (3.2.1.3(3.2.1.3)) at regularly
spaced intervals
Note 1 to entry: See Figure 13Figure 13.
Figure 13
3.2.4.2
double-sided synchronous belt
synchronous belt (3.2.1.1(3.2.1.1)) with teeth located on both sides of the pitch line (3.2.1.3(3.2.1.3)) at
regularly spaced intervals
Note 1 to entry: See Figure 14Figure 14.

a) Staggered double-sided synchronous belt

b) Symmetrical double-sided synchronous belt

a) Staggered double-sided synchronous belt
b) Symmetrical double-sided synchronous belt
Figure 14
3.2.5 3.2.5 Teeth
3.2.5.1
tooth
generally transverse element protruding from the root of the belt which have the profile necessary to mesh
with the grooves (3.3.2.1(3.3.2.1)) in a synchronous pulley (3.3.1.1(3.3.1.1))
Note 1 to entry: See Figure 15Figure 15.

Figure 15
3.2.5.2
tip line
line joining the tips of the belt teeth
Note 1 to entry: See Figure 16Figure 16.

Figure 16
3.2.5.3
root line
line joining the roots between the belt teeth
Note 1 to entry: See Figure 17Figure 17.

Figure 17
3.2.5.4
tooth height
h
t
distance between the tip line (3.2.5.2(3.2.5.2)) and the root line (3.2.5.3(3.2.5.3))
Note 1 to entry: See Figure 18Figure 18.

Figure 18
3.2.5.5
flank
area defined by the width (3.2.1.6(3.2.1.6)) of the belt tooth (3.2.5.1(3.2.5.1)) and the portion of the tooth
section contained between the tooth tip radius and the tooth root radius or, if there is no tooth tip radius,
contained between the tip line (3.2.5.2(3.2.5.2)) and the tooth root radius
Note 1 to entry: See Figure 19Figure 19.

a)
b)
a)
b)
Figure 19
3.2.5.6
working flank
flank (3.2.5.5(3.2.5.5)) of a belt tooth (3.2.5.1(3.2.5.1)) in contact with the pulley groove flank when it
is transmitting power
Note 1 to entry: See Figure 20Figure 20.

Figure 20
3.2.5.7
non-working flank
flank (3.2.5.5(3.2.5.5)) of the tooth (3.2.5.1(3.2.5.1)) opposite the working flank (3.2.5.6(3.2.5.6))
Note 1 to entry: See Figure 21Figure 21.

Figure 21
3.2.5.8
radius at tooth tip
r
a
radius of a generally curved section of a belt tooth (3.2.5.1(3.2.5.1)) that connects the tooth flank
(3.2.5.5(3.2.5.5)) with the tip line (3.2.5.2(3.2.5.2))
Note 1 to entry: See Figure 22Figure 22.

Figure 22
3.2.5.9
radius at tooth root
r
r
radius of a curve connecting the tooth (3.2.5.1(3.2.5.1) )flank (3.2.5.5(3.2.5.5)) with the root line
(3.2.5.3(3.2.5.3))
Note 1 to entry: See Figure 23Figure 23.
Figure 23
3.2.5.10
width at tooth root
S
linear distance between the theoretical points of intersection of the tooth (3.2.5.1(3.2.5.1) )flanks
(3.2.5.5(3.2.5.5)) with the root line (3.2.5.3(3.2.5.3)) when the belt is straight
Note 1 to entry: See Figure 24Figure 24.

Figure 24
3.2.5.11
tooth angle

included angle between the flanks (3.2.5.5(3.2.5.5)) of the belt tooth (3.2.5.1(3.2.5.1))
Note 1 to entry: See Figure 25Figure 25.
Figure 25
3.3 3.3 Pulleys
3.3.1 3.3.1 General
3.3.1.1
synchronous pulley
pulley with generally transverse grooves (3.3.2.1(3.3.2.1)) equally spaced around its circumference
Note 1 to entry: See Figure 26Figure 26.
Figure 26
3.3.1.2
pitch reference cylinder
imaginary cylindrical surface, coaxial to a pulley, located at the point at which the circular pitch of the pulley
is equal to the pitch of the belt it is used with
Note 1 to entry: See Figure 27Figure 27.

Figure 27
3.3.1.3
pitch circle
section of a pitch reference cylinder (3.3.1.2(3.3.1.2)) with a plane perpendicular
...

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