ISO 9981:2020

INTERNATIONAL ISO
STANDARD 9981
Third edition
2020-06
Belt drives — Pulleys and V-ribbed
belts for the automotive industry —
PK profile: Dimensions
Transmissions par courroies — Poulies et courroies striées pour la
construction automobile — Profil PK: Dimensions
Reference number
©
ISO 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Pulleys . 2
5.1 Groove dimensions and tolerances . 2
5.2 Minimum effective diameter . 4
5.3 Tolerances on finished pulley . 4
5.3.1 Checking conditions . 4
5.3.2 Groove-to-groove diameter tolerances . 5
5.3.3 Radial and axial circular run-out . 5
5.3.4 Diameter over balls. 5
5.3.5 Groove finish. 5
5.4 Pitch diameter, d . 5
p
5.5 Designation of pulleys. 5
6 Belts . 6
6.1 Belt dimensions . 6
6.2 Measurement of the effective belt length . 8
6.2.1 Elastic belt . 8
6.2.2 Measuring fixture . 8
6.2.3 Measuring force . 8
6.2.4 Procedure . 8
6.3 Designation of belts . 9
Bibliography .10
Foreword
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electrotechnical standardization.
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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).
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts),
Subcommittee SC 1, Friction.
This third edition cancels and replaces the second edition (ISO 9981:1998), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the normative references list has been updated;
— clarification has been made where the standard is not for elastic belts;
— 5.3.5 has been revised to reference ISO 254 for pulley roughness;
— the current roughness values have been removed;
— the maximum pulley groove radius (Table 2) has been specified.
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

Introduction
A V-ribbed belt drive is composed of an endless belt with a longitudinally ribbed traction surface which
engages and grips, by friction, pulley grooves of similar shape. The belt ribbed surface fits the pulley
grooves to make nearly total contact.
INTERNATIONAL STANDARD ISO 9981:2020(E)
Belt drives — Pulleys and V-ribbed belts for the automotive
industry — PK profile: Dimensions
1 Scope
This document specifies the principal dimensional characteristics of V-ribbed pulley groove profiles,
together with the corresponding endless V-ribbed belts of PK profile which are used predominantly for
automotive accessory drive applications.
This document does not apply to the complete array of V-ribbed belts and pulleys of PH, PJ, PK, PL and
PM profile for industrial and other non-autom
...