ISO 4378-1:2017

Overview

ISO 4378-1:2017 - Plain bearings - Terms, definitions, classification and symbols - Part 1: Design, bearing materials and their properties defines the common terminology, classification schemes and symbols used for plain (sliding) bearings. Prepared by ISO/TC 123/SC 6 (secretariat: JISC), this fourth edition updates the vocabulary and classifications used by designers, manufacturers and engineers to reduce ambiguity in specification, documentation and communication about plain bearings and bearing materials.

Key topics covered

• Scope and purpose: specifies the most commonly used terms relating to plain bearing design, bearing materials and material properties; short forms are given where unambiguous.
• General definitions: clear definitions for “bearing”, “plain bearing”, and “plain bearing unit”.
• Classification by load: statically loaded vs. dynamically loaded plain bearings.
• Load-direction classification: journal (radial), thrust (axial) and journal-thrust (flanged) bearings.
• Lubrication and operating modes: hydrodynamic, hydrostatic, hydrodynamic gas (air), hydrostatic gas, squeeze-film, hybrid, solid-film lubricated, unlubricated, self-lubricating, porous/sintered (oil-impregnated) bearings, foil bearings and spiral-groove systems.
• Design and geometry classifications: circular cylindrical, profile-bore, lobed, pad thrust, taper-land, tilting-pad (journal and thrust), floating bush, plain bearing assemblies (pedestal/pillow block, flanged) and self-aligning/offset arrangements.
• Structural elements and multilayer linings: half-bearings, bushes, flanged half-bearings, multilayer bearings, backing layers, lining/overlay/running‑in layers, interlayers (bonding), protective layers and thrust washers.
• Symbols and short forms: standardised abbreviations for common terms to improve clarity in drawings and specifications.

Practical applications and who uses it

ISO 4378-1:2017 is a foundational reference for:

• Mechanical design and rotating equipment engineers specifying plain bearings and bearing assemblies
• Bearing manufacturers and material suppliers developing multilayer and self-lubricating liners
• Tribologists and lubrication specialists evaluating lubrication regimes (hydrodynamic, hydrostatic, solid-film, etc.)
• Procurement, quality and standards teams creating unambiguous product specifications and test reports
• Maintenance and reliability engineers documenting repairs and replacement parts

Using unified terminology from ISO 4378-1 reduces misinterpretation in design documents, improves supplier communication, and supports international trade by harmonising plain bearing descriptions.

Related standards

• ISO 4378 is a multi-part series; a complete list of parts in the ISO 4378 series is available on the ISO website. (ISO 4378-1 contains no normative references.)

Keywords: ISO 4378-1:2017, plain bearings, bearing materials, bearing design, classification, terms and definitions, hydrodynamic bearing, hydrostatic bearing, self-lubricating bearing, plain bearing assembly.