BS 978-2:1952

Co-operating organizations
Foreword
Section one: General
1 Scope
2 Terminology and notation
3 Range of standard modules
Section two: Tooth form and proportions
4 Wheels driving pinions
5 Driven pinions
6 Wheels and pinions for trains in which the pinion may
   act sometimes as the driver and sometimes as the
   driven member
7 Contrate gears
Section three: Tolerances (in millimetres)
Appendices
A Notes on the derivation of cycloidal gears where the
   wheel drives the pinion
B Notation

Forms and proportions of spur gears for instruments and clockwork mechanisms from 0.070 modules to 1.000 module. Provisions for contrate gears, derivation of cycloidal gears (where the wheel drives the pinions), tolerances.

This part applies to cycloidal type spur gears for spring or weight-driven mechanisms in which:

1. the pinion is the driven member, or
2. the pinion is required to act sometimes as the driver and sometimes as the driven member.

For integrating electricity meters the particular form of gear specified herein is not necessary and it is recognised that other existing forms of gear will continue to be used.