ISO 4378-5:2009

Overview

ISO 4378-5:2009 - "Plain bearings - Terms, definitions, classification and symbols - Part 5: Application of symbols" specifies the practical application of the general symbols defined in ISO 4378-4 for the calculation, design and testing of plain bearings. It standardizes how symbols, basic characters and additional signs (subscripts and superscripts) are used in engineering documentation, calculation formulas and test reports for journal bearings, thrust bearings, tilting‑pad bearings and hydrostatic bearings. The standard also clarifies conventions such as positive angles and rotation (left‑hand/anticlockwise).

Key Topics

• Symbol conventions and notation: Use of Roman and Greek alphabet symbols, plus rules for subscripts and superscripts (additional signs), distinguishing basic characters from composite symbols.
• Scope of symbols: A comprehensive list of symbols commonly used in plain bearing work - for example:
  • C for bearing clearance (radial/diametral), with subscripts for mean, max, min and thermal/elastic changes;
  • D and d for diameters and characteristic sizes (bearing, journal, groove, pad, orifice);
  • F for bearing forces and loads (axial, radial, dynamic, static) and related parameters;
  • h for lubricant film thickness and related relative values;
  • f for coefficients of friction and friction parameters;
  • c, k, d for stiffness and damping coefficients, with indices for inner/outer or directional components.
• Application rules: How symbols are combined for calculations, manufacturing specifications and testing data, and the recommended positive directions for rotations and angular velocities.
• Completeness caveat: The listing is extensible - not all alphabet letters are used and the set may be enlarged as needed.

Applications

ISO 4378-5 is used by:

• Bearing designers and mechanical engineers for consistent notation in design calculations and CAD/CAE models.
• Tribologists and test laboratories for standardized reporting of test results (clearances, film thickness, friction, damping).
• Technical authors and standards writers preparing specifications, drawings and user manuals.
• Procurement and quality assurance teams to ensure unambiguous component requirements and acceptance criteria.

Using ISO 4378-5 reduces misinterpretation across international teams and preserves clarity in engineering calculations, manufacturing data and test reports for plain bearings.

Related Standards (if applicable)

• ISO 4378-1: Design, bearing materials and their properties
• ISO 4378-2: Friction and wear
• ISO 4378-3: Lubrication
• ISO 4378-4: Basic symbols (source of general symbol definitions)
• Note: ISO 4378-5:2009 replaces ISO 4378-4:1997 and ISO 7904-2:1995 for symbol application.