BS 4582-1:1970

This standard BS 4582-1:1970 Specification for fine pitch gears (metric module) is classified in these ICS categories:

• 21.200 Gears

This British Standard relates to involute spur, helical and crossed helical gears, having modules of one millimetre and finer, in four accuracy grades. Examples of application are:

Class A. Astronomical apparatus and scientific instruments; colour printing machinery; control systems (when multiple trains of gears are involved this grade would generally be used for low speed components where the effect of positional accuracy is important).

Class B. Navigational instruments; high speed components of control systems where quietness and smooth running are essential; machine tool speed control; photo­ graphic instruments.

Class C. General purpose instruments; accounting and calculating machinery; counters; clockwork mechanisms.

Class D. Textile machinery; switch operating gear; clockwork mechanisms where accuracy is not the primary consideration.

It is recommended that all spur, helical and crossed helical gears for use in horology should be produced to this British Standard, with the possible exception of gears for weight or spring-driven mechanisms in which the pinion is the driven member and has 12 or fewer teeth. In such cases it may be preferable to use cycloidal type spur gears, conforming to BS 978, Part 2†.

Examples of calculation are given in Appendix B.

Covers gears having modules of 1 mm and less including first and second preferences. Two basic racks (one with backlash allowance); modification of addendum and centre distance to suit various conditions. Four grades of accuracy with elemental and dual flank composite test tolerances. Appendices give information on single flank testing, calculation of measuring pin dimensions and examples of calculations for various design conditions. Metric equivalent of BS 978-1.