ISO 17396:2017

INTERNATIONAL ISO
STANDARD 17396
Second edition
2017-11
Synchronous belt drives — Metric pitch
— Tooth profiles T and AT endless and
open ended belts and pulleys
Transmissions synchrones par courroies — Pas métrique — Poulies et
courroies dentées sans fin ou à bout libre à dents de profil T ou AT
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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ii © ISO 2017 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Belt profile systems . 2
5 Belt nomenclature . 2
6 Pulley profile systems . 2
7 Pulley nomenclature . 3
8 Belt profile systems T and AT . 4
8.1 Belt profile systems T and AT — General . 4
8.2 Profile system T — Belt tooth dimensions and tolerances . 4
8.3 Profile system AT — Belt tooth dimensions and tolerances . 5
9 Belt widths and tolerances. 5
10 Pitch length measurement . 6
10.1 Endless belts manufactured in circular moulds . 6
10.2 For very long endless belts and open belts . 7
10.3 Total measuring forces . 7
10.4 Procedures . 8
10.4.1 For endless belts manufactured in circular moulds . 8
10.4.2 For very long endless belts and open belts . 8
10.5 Belt length tolerances . 8
11 Pulleys .10
11.1 General profile system T .10
11.1.1 General.10
11.1.2 Profile system T — Pulley groove dimensions and tolerances .10
11.1.3 Profile system T — Pulley groove profile .11
11.1.4 Profile system T — Pulley diameters .11
11.1.5 Profile system T — Pulley width .12
11.2 General profile system AT.13
11.2.1 General.13
11.2.2 Profile system AT — Pulley groove profile dimensions and tolerances .13
11.2.3 Profile system AT — Pulley groove profile .14
11.2.4 Profile system AT — Pulley diameters .14
11.2.5 Pulley system AT — Pulley width.14
Annex A (normative) Pulley tolerances .16
Foreword
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described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
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URL: 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 second edition cancels and replaces the first edition (ISO 17396:2014), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— root diameter specifications for AT series pulleys (Figure 6 and Table 12) have been added.
iv © ISO 2017 – All rights reserved

INTERNATIONAL STANDARD ISO 17396:2017(E)
Synchronous belt drives — Metric pitch — Tooth profiles T
and AT endless and open ended belts and pulleys
1 Scope
This document specifies the principal characteristics of synchronous endless and open belts and pulleys
of the profile systems T and AT for use in synchronous belt drives for mechanical power transmission
and where positive indexing or synchronization can be required.
NOTE Synchronous belt drives have been known by various titles in the past: for example, timing belt drives,
positive belt drives, gear belt drives.
The principal belt and pulley characteristics include
a) nominal belt tooth dimensions,
b) belt tooth pitch spacing,
c) belt length and width dimensions,
d) belt length measurement specifications,
e) pulley groove dimensions and tolerances,
f) pulley diameter and width dimensions and tolerances, and
g) pulley quality specification.
The belts of the profile systems T and AT are made of polyurethane with high-tension fine steel cord
tension members in most cases. As far as certain forces are given in this document, these values are
only valid for these kinds of belt. For polyurethane belts with different tensile cords, i.e. aramid or
rubber belts reinforced with glass fibre, the values can be different. It is intended that the user and
the manufacturer agree about suitable values. Open belts made of thermoplastic polyurethane can be
spliced to work as endless belts in conveyor applications. In this case, the tolerances are not valid for
the splicing area of the endless spliced belt.
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 254, Belt drives — Pulleys — Quality, finish and balance
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Belt profile systems
Eight belt profiles for synchronous drives are standardized.
Profile system T: Profile system AT:
—  profile T2,5 —  profile AT3
—  profile T5 —  profile AT5
—  profile T10 —  profile AT10
—  profile T20 —  profile AT20
5 Belt nomenclature
A belt is designated by a combination of numbers and letters as follows:
a) the width, in millimetres;
b) the profile system;
c) the pitch, in millimetres;
d) the belt pitch length, in millimetres (and add the number of teeth in brackets, if required);
e) double-sided belts are designated by adding D or D before the profile system letter: D if the
G T G
tooth position is opposite Gap; D if the tooth position is opposite Tooth;
T
f) open belts are designated by adding the letter “M” behind the length; for spliced belts, use the
letter “V.”
EXAMPLE 1 A metric synchronous belt of 10 mm pitch, profile system T, 50 mm wide, and 1 400 mm in pitch
length is designated as follows:
— for a single-sided belt: 50 - T10 - 1 400;
— for a double-sided belt: 50 - D - T10 - 1 400 or 50 - D - T10 - 1 400.
G T
EXAMPLE 2 A metric synchronous belt of 5 mm pitch, profile system AT, 25 mm wide, and 500 mm in pitch
length (number of teeth = 100) is designated as follows:
— for a single-sided belt: 25 - AT5 - 500 (100 t);
— for double-sided belt: 25 - D - AT5 - 500 (100 t) or 25 - D - AT5 - 500 (100 t).
G T
EXAMPLE 3 An open metric synchronous belt of 5 mm pitch, profile system AT, 25 mm wide, and 50 000 mm
in pitch length is designated as
25 - AT5 - 50 000 - M.
6 Pulley profile systems
Eight pulley profiles for synchronous drives are standardized.
2 © ISO 2017 – All rights reserved

Profile system T: Profile system AT:
—  profile T2,5 —  profile AT3
—  profile T5 —  profile AT5
—  profile T10 —  profile AT10
—  profile T20 —  profile AT20
7 Pulley nomenclature
A pulley for a synchronous drive is identified by the number of grooves, the groove pitch and profile,
and the width. It is designated, as is the belt, by a combination of numbers and letters as follows:
a) the letter “P”, which indicates a pulley;
b) the number of grooves;
c) the profile system;
d) the groove pitch, in millimetres;
e) the width, in millimetres.
EXAMPLE A pulley for a metric toothed belt which has 20 mm pitch and 30 grooves with a nominal width of
50 mm is identified as follows:
— for T-profile system pulley: P30 - T20 - 50;
— for AT-profile system pulley: P30 - AT20 - 50.
...