ISO 1122-1:1998

Overview

ISO 1122-1:1998 - Vocabulary of gear terms, Part 1: Definitions related to geometry - is an international standard that provides unified, rigorous geometrical definitions for gear terminology. Prepared by ISO/TC 60 (Gears), Subcommittee SC 1, this second edition (1998) replaces the 1983 edition and is intended as a definitive vocabulary to remove ambiguity in international gear engineering, documentation and translation. It focuses on ordinary gears with constant ratio and deliberately excludes non‑standard types (for example, elliptical gears).

Key topics

The standard establishes precise geometric definitions used across design, manufacturing and standards documents. Major topics include:

• Kinematic relationships and axis positions: parallel gears, bevel (intersecting) gears, crossed (skewed) gears, centre distance, shaft angle.
• Gear assemblies: gear pair, train of gears, epicyclic/planetary gear trains and component names (sun gear, annulus/crown, planet gear, planet carrier).
• Mating gears and roles: pinion, wheel, driving gear, driven gear, idler gear.
• Terminology rules: how terms are chosen in each language to reflect the geometric definition and guidance to prefer the definition meaning over literal translation.
• Editorial changes from earlier edition: additions (e.g., constant chord), deletions of obsolete or non‑practical terms, and splitting of previously combined definitions to reduce ambiguity.

(ISO 1122‑1 emphasizes clear, rigorous geometric definitions rather than extended tutorials or workshop shortcuts.)

Practical applications

ISO 1122-1 is used to ensure consistent, unambiguous gear terminology across:

• Technical drawings, specifications and procurement documents
• Gear design and engineering reports where precise gear geometry terms are required
• Manufacturing and quality control instructions to avoid misinterpretation of geometric features
• Standards development, testing codes and conformity assessment
• Multilingual technical translation - translators are advised to rely on definitions rather than literal term transposition

Using ISO 1122-1 improves communication between designers, manufacturers, standards committees and international partners, reducing errors and rework caused by inconsistent terminology.

Who should use it

• Gear designers and mechanical engineers
• Technical writers and documentation teams
• Standards committees and regulatory bodies (ISO/TC 60 participants)
• Quality and inspection engineers
• Technical translators and localization specialists

Related standards

• ISO 1122-2 - Part 2: Definitions related to worm gear geometry (companion document referenced by ISO 1122-1)
• Other ISO gear standards produced by ISO/TC 60 (for design, measurement and testing)

Keywords: ISO 1122-1, gear vocabulary, gear terminology, gear geometry, geometrical definitions, ISO gear standard, planetary gear, pinion, centre distance.