ISO 6525:2018

Overview - ISO 6525:2018 (Plain bearings, ring type thrust washers)

ISO 6525:2018 specifies the dimensions and tolerances for ring type thrust washers made from strip, intended for general‑purpose use with wrapped bushes as specified in ISO 3547. The standard covers unsplit ring thrust washers that fit into a housing recess to accept axial thrust and provide axial location for a rotating shaft. It applies to washers with inside diameters from 6 mm to 80 mm and is aimed at harmonizing sizes to reduce tooling costs (not all sizes are necessarily stocked).

Key topics and technical requirements

• Scope and definitions - Clear terms (e.g., ring type thrust washer) and symbolic notation for size parameters.
• Dimensions and tolerances - Standardized nominal values for inside/outside diameters, washer thickness, pitch circle and dowel hole positions; tolerances are specified (including reference to fits such as G10 for certain diameters).
• Recess and location - Washers are normally located in a housing recess and retained against rotation by a dowel (alternatively lug or tab). Recess corners should be sharp or undercut to avoid interference with washer corners.
• Oil grooves - Provision for oil grooves by agreement between user and manufacturer. Grooves primarily feed lubricant; typical grooving arrangements are illustrated. For bimetallic linings, groove depth should preferably be less than the lining thickness. Sharp groove edges must be removed.
• Flatness - Ungrooved washers must meet a flatness requirement: they shall slide between parallel plates set at e + p, where p = 0.10 mm for washers up to 80 mm outside diameter and p = 0.12 mm above that size. Flatness is not specified for grooved washers due to distortion from grooving.
• Edges and finishing - All sharp edges shall be removed; finishing and deburring requirements are stated to ensure assembly safety and fit.

Applications and who uses this standard

ISO 6525:2018 is relevant to:

• Bearing manufacturers and fabricators of plain bearings and thrust washers
• Design and mechanical engineers specifying thrust surfaces in rotating machinery
• OEMs in automotive, industrial gearboxes, pumps, compressors and agricultural equipment
• Purchasing and quality assurance teams ensuring interchangeability and correct tolerances
• Toolmakers and production planners aiming to standardize tooling and reduce costs

Practical benefits include improved interchangeability with wrapped bushes (ISO 3547), predictable assembly fits, simplified procurement, and lower tooling/production costs.

Related standards

• ISO 3547 (all parts) - Wrapped bushes (explicitly referenced for compatibility)
• Prepared by ISO/TC 123 (Plain bearings), Subcommittee SC 3 (Dimensions, tolerances and construction details)

Keywords: ISO 6525:2018, plain bearings, ring type thrust washers, dimensions and tolerances, wrapped bushes, ISO 3547, oil grooves, flatness, dowel, thrust washers.