BS 721-2:1983

This Part of BS 721 specifies the requirements for worm gearing based on axial modules. Four classes of gear are specified, which are related to function and accuracy.

This Part applies to worm gearing comprising cylindrical involute helicoid worms and wormwheels conjugate thereto. It does not apply to pairs of cylindrical gears connecting non-parallel axes known as crossed helical gears.

Appendix A gives some typical wheel rim sections together with methods of attachment. Appendix B gives examples of calculations using the formulae given in the standard. Provision is made in appendix C for a method of application of existing hobs designated in terms of axial pitch.

NOTE 1. Worm gearing designed to this standard is not to be regarded as irreversible.

NOTE 2. The titles of the publications referred to in this standard are listed on the inside back cover.

Applies to tooth form, dimensions of gearing, tolerances for four classes of gears according to function and accuracy, calculation of load capacity and information to be given on drawings. Provides examples of load calculations.