BS 978-3:1952

Co-operating organizations
Foreword
Specification
Section one: General
1 Scope
2 Terminology and notation
Section two: Form of gear tooth
3 Form of gear tooth
4 Tooth spiral
5 Addendum and dedendum
6 Caliper settings
Section three: Permissible errors and tolerances
7 Pitch errors
8 Tooth thickness tolerance
Appendix
Notation
Chart
1 Interference factor (Q) for bevel gears

Form, proportions of machine cut conical gears connecting intersecting shafts in pitch range 20 to 80 D.P. Straight or curved teeth with normal pressure angle 20 at pitch cone. Addendum modification, permissible errors and tolerances for Class A, Class B gears.

This part applies to machine cut conical gears, of the classes described below, connecting intersecting shafts and having pitches from 20 to 80 DP. The teeth shall have a normal pressure angle of 20° at the pitch cone and they may be straight or curved (see Figure 1 to Figure 4). The standard provides for Class A gears for use where a high degree of accuracy is required, and Class B gears for other applications. For integrating electricity meters the particular form of gear herein specified is not necessary and it is recognised that other existing forms of gear will continue to be used.