ISO 12240-1:1998

ISO 12240-1:1998 - Overview

ISO 12240-1:1998 is the International Organization for Standardization specification for radial spherical plain bearings. This Part 1 defines the accepted dimension series, manufacturing tolerances and radial internal clearances that producers and designers must use when producing or specifying radial spherical plain bearings. The standard is intended to allow the design of bearings using a wide choice of sliding material combinations and applies to finished bearings prior to any coating, plating, ring splitting or ring fracturing. Note: bearings for airframe applications are excluded.

Key topics and technical requirements

• Dimension series and profiles: the standard provides dimension series (for example series E, G, C, K, H, W) with nominal sizes and geometric arrangements to guide consistent bearing geometry.
• Tolerances: prescribed tolerances for inner and outer ring dimensions and form (tables in the document) ensure interchangeability and predictable fit.
• Radial internal clearance: definitions and tabulated clearance ranges (grouped values such as Group 2, Group N, Group 3) specify allowable relative displacement between inner and outer rings. The standard recommends multiple angular-direction measurements and, for large bearings, determination via mean sphere diameters before assembly.
• Surface treatment note: the stated tolerance values apply to finished bearings before surface coatings; surface-treated bearings may show slight deviations from those tolerance values.
• Design flexibility: manufacturers are not required to use the illustrated designs but must comply with the specified dimensions, tolerances and clearances.
• Normative references: the standard references related documents such as ISO 582 (chamfer dimensions), ISO 1132-1 (tolerances terms) and ISO 6811 (vocabulary).

Applications and practical value

ISO 12240-1 is used to:

• Standardize bearing geometry and interchangeability in mechanical designs.
• Provide basis for procurement specifications and quality control acceptance criteria.
• Support bearing selection and housing/shaft interface design in machinery.
• Ensure compatibility when selecting sliding material combinations for tribological performance.

Typical sectors that benefit include machine design, heavy equipment, hydraulics and general industrial engineering where radial spherical plain bearings are used to accommodate angular misalignment and oscillatory motion.

Who uses this standard

• Bearing manufacturers and component designers
• Mechanical and product engineers
• Procurement, inspection and quality assurance teams
• Maintenance engineers specifying replacement parts

Related standards

• ISO 12240 (other parts): Part 2 (angular contact), Part 3 (thrust bearings), Part 4 (rod ends)
• ISO 582, ISO 1132-1, ISO 6811

Keywords: ISO 12240-1:1998, radial spherical plain bearings, dimensions, tolerances, radial internal clearance, bearing design, sliding material combinations, bearing standards.