PD 6457:1970

Foreword
1. Introduction
2. Terminology, definitions and notation
3. Tooth design (general)
4. Tooth design: value of sigma x
5. Tooth design: division of sigma x between pinion
     and wheel
6. Limiting values of sigma x
7. Limits to the individual values of x1 and x2
8. Application to internal tooth gearing
9. Centre distance modification coefficient
Appendix
A. Calculations and formulae
A.1 Calculation sequence and basic design formulae
A.2 Relative values for x1 and x2
A.3 Tooth thickness formulae
A.4 Base tangent span dimension
A.5 Diameter over gauge rolls or balls, of diameter dR
A.6 Tip diameter formulae
A.7 Root diameter formulae
A.8 Minimum values of x required for avoiding undercut
     tooth profiles
Tables
1. Dimensions of standard long addendum spur pinions
     in terms of unit module or diametral pitch
1A. Centre distances, in terms of unit module or
     diametral pitch, at which standard long addendum
     spur pinions and wheels having x2 = 0 engage without
     backlash
2. Corresponding values of sigma x, y and alpha w for
     alpha n = 20 deg
Figure
1. Examples of addendum modification
Charts
1. Limiting values of the sum of addendum modification
     coefficients applicable to external tooth spur and
     helical gear pairs
2. Limiting values for the addendum modification
     coefficient applicable to an external spur or
     helical gear

Provides guidance on the modification to the teeth of involute spur and helical gears with the object of making provision for design latitude enabling standard cutting tools to be used to their best advantage. Covers terminology, definitions and notation, tooth design, limiting values, application to internal tooth gearing and centre distance modification coefficient.