What is ISO 14521 about?

ISO 14521 specifies formulae 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 14521.

The load rating and design procedures are only valid for tooth surface sliding velocities, vg, less than or equal to 25 m/s and contact ratios greater than 2,1. For wear, load rating and design procedures are only valid for tooth surface sliding velocities that are above 0,1 m/s. The rules and recommendations for the dimensioning, lubricants or materials selected by ISO 14521 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 14521 is intended for use by experienced gear designers who can make informed judgements concerning factors. It is not intended for use by engineers who lack the necessary experience.

Note: The geometry of worm gears is complex, therefore the users of ISO 14521 is encouraged to make sure that a valid working geometry has been established.

Who is ISO 14521 for?

ISO 14521 on the calculation of load capacity of worm gears is relevant to:

Manufacturer of cylindrical worm gears
Suppliers and customers of cylindrical worm gears
Mechanical engineers

Why should you use ISO 14521?

A worm gear is a gear consisting of a shaft with a spiral thread that engages with and drives a toothed wheel.

ISO 14521 provides information on worm gear load capacity rating criteria, required date for calculation, forces, speeds and parameters for the calculation of stresses, efficiency and power loss, wear load capacity, surface durability (pitting resistance), tooth root strength, temperature safety factor, determination of the wheel bulk temperature of cylindrical worm gears

As a user of ISO 14521, you will be able to calculate the load capacity of cylindrical worm gears. With ISO 14521 you can also determine the static and fatigue strength of worm gears. ISO 14521 helps in improving the quality and strength of worm gear. ISO 14521 can assist in reducing the wear and tear of worm gear. Overall with ISO 14521, you can build consumer trust and confidence in the product.

What’s changed since the last update?

PD ISO/TS 14521:2020 supersedes PD ISO/TR 14521:2010, which has been withdrawn.

The main changes compared to the previous edition are as follows:

The original Clause 6 which focused on geometry has been deleted and ISO/TR 10828 has been referenced

PD ISO/TS 14521:2020

Gears. Calculation of load capacity of worm gears

Current, Under Review

Published:

31 May 2020