BS 978-2 is a British Standard that discusses gears for instruments and clockwork mechanisms.
BS 978-2 is the second part of the BS 978 multi-series, and relates to spur and helical gears with pitches of 0.15 to 0.7 mm module inclusive, the basic rack of the system has a normal tooth profile composed of two circular arcs.
BS 978-2 on double circular arc type gears is useful for:
The cycloidal gear profile is a form of toothed gear used in mechanical clocks, rather than the involute gear form used for most other gears.
BS 978-2 walks you through the normal modules, terminology and notation, form of tooth, tolerances, and cutters of double circular arc type gears.
Detailed diagrams and tables have been provided in BS 978-2 to illustrate the shapes and dimensions of double circular arc type gears.
BS 978-2 guideline helps you to follow best practices when designing and manufacturing double circular arc type gears. This lets you demonstrate the efficiency and reliability of your double circular arcs gears.