ISO/TR 14521:2010

ISO/TR 14521:2010 specifies equations for calculating the load capacity of cylindrical worm gears and covers load ratings associated with wear, pitting, worm deflection, tooth breakage and temperature. Scuffing and other failure modes are not covered by ISO/TR 14521:2010.
The load rating and design procedures are valid for sliding velocities over tooth surfaces of up to 25 m/s and contact ratios equal to or greater than 2,1. For wear, sliding velocities over tooth surfaces are not below 0,1 m/s.
The rules and recommendations for the dimensioning, lubricants or materials selected by ISO/TR 14521:2010 only apply to centre distances of 50 mm and larger. For centre distances below 50 mm, method A applies.
The choice of appropriate methods of calculation requires knowledge and experience. ISO/TR 14521:2010 is intended for use by experienced gear designers who are able to make informed judgements concerning factors. It is not intended for use by engineers who lack the necessary experience.
The geometry of worm gears is complex, therefore the user of ISO/TR 14521:2010 is encouraged to make sure that a valid working geometry has been established.