Final Draft
International StandardISO/FDIS 21771-2
Cylindrical involute gears and gear pairs — Part 2: Calculation and measurement of tooth thickness and backlash
Reference number
ISO/FDIS 21771-2
ISO/FDIS 21771-2
Edition 1
© ISO 2025
Final Draft International Standard
Abstract
This standard establishes the calculation procedures for determining specification limits for external and
internal cylindrical involute gearing with constant gear ratio when the desired tooth thickness is known.
This standard also shows the relationships between backlash and the tooth thickness, centre distance,
and tooth deviations in a pinion and gear mesh.