ISO 6811:1998

Overview - ISO 6811:1998 (Spherical plain bearings - Vocabulary)

ISO 6811:1998 is an international vocabulary standard that defines general terms and definitions used for spherical plain bearings (rotules lisses). Prepared by ISO/TC 4 (Rolling bearings), SC 7 (Spherical plain bearings), this second edition (1998) replaces the 1983 edition. The standard covers bearings, bearing parts and features, relative movements, contact angles and rod ends, and includes figures and an alphabetical index to support consistent technical language across design, manufacture and documentation.

Key topics and structure

The standard is organized to provide a systematic, unambiguous vocabulary for use in engineering and standards work:

• Scope: terms and definitions relevant to spherical plain bearings, movements, angles and rod ends.
• Multilingual coverage: official ISO terms are given in English, French and Russian; equivalent German terms are published under DIN responsibility (German equivalents are informative, not ISO terms).
• Clause structure: clause 3 lists terms and definitions (grouped and sub-grouped); clause 4 contains figures linking index numbers to terms; an alphabetical index cross-references terms to entry numbers.
• Numbering system: groups (two-digit), subgroups (four-digit) and entries (six-digit) provide systematic reference identifiers for each term.
• Representative technical notions included: types of spherical plain bearings (radial, thrust, radial contact with nominal contact angle 0°, angular-contact radial up to 30°, axial contact τ = 90°, angular-contact thrust >30° and <90°), bearing features (bearing bore, outside surface), and rod-end terminology.
• Illustrations: figures show typical forms (simplified) and indicate the index numbers of relevant terms.

Practical applications - who uses ISO 6811:1998

ISO 6811:1998 is primarily used to ensure consistent terminology in:

• Bearing designers and manufacturers for clear product descriptions, drawings and catalogs.
• Procurement and specification engineers to avoid ambiguity in purchase orders and contracts.
• Standards writers and technical editors who prepare linked or complementary bearing standards (e.g., ISO 4378-1 references).
• Maintenance, quality and testing personnel who need consistent naming for components and failures.
• Translators and international teams requiring precise multilingual equivalents for global trade and documentation.

Using ISO 6811 helps reduce misinterpretation in technical documents, supports interoperability of bearings in assemblies, and improves clarity in international specifications.

Related standards

• ISO 4378-1 - referenced for general bearing definitions.
• Work developed by ISO/TC 4 – Rolling bearings, Subcommittee SC 7 – Spherical plain bearings; German equivalents published by DIN.

Keywords: ISO 6811:1998, spherical plain bearings, vocabulary, bearing terminology, radial spherical plain bearing, thrust spherical plain bearing, rod ends, bearing features, contact angle.