Overview - ISO 6626-1:2024 (Piston rings, Part 1)
ISO 6626-1:2024 specifies the essential dimensional features and related requirements for coil‑spring loaded oil control piston rings made of cast iron. It covers the common ring types (DSF‑C, DSF‑CNP, SSF, GSF, DSF, DSF‑NG and SSF‑L) for reciprocating internal combustion engines used in road vehicles and other applications. The standard applies to ring diameters from 60 mm to 200 mm and addresses typical axial widths (3 mm–8 mm, with specific tables for 4.75 mm / 3/16 in).
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Key technical topics and requirements
- Types and designations: Defines cross‑sectional types (DSF‑C, DSF‑CNP, SSF, GSF, DSF, DSF‑NG, SSF‑L) and example designation formats.
- Dimensional tables and figures: Comprehensive tables (Tables 8–25) and figures (1–11) specifying geometry, ring widths, land widths and reference planes.
- Materials: Recommends cast iron material classes (Class 10 per ISO 6621‑3 as baseline; Classes 20–50 for special uses).
- Coil spring features: Essential coil spring geometry, latch pin locations, excursion (extended gap), material and fixing methods (Figures 12–16).
- Oil drainage: Slot and hole arrangements, lengths, diameters and numbers to control oil evacuation from the cylinder wall.
- Surface treatments: Chromium plating details for types DSF‑C and DSF‑CNP, including plating thickness and peripheral edge treatment at ring gaps.
- Contact mechanics: Tangential force, normalized tangential force, and nominal contact pressure classes (historical classes moved to Annex A); specified tolerances and force factors.
- Common features: Spring groove and land offsets, assembly and gap management (selected closed gap examples appear).
Practical applications and typical users
Who uses ISO 6626-1:2024:
- Engine designers specifying oil control ring geometry for new engines
- Piston ring manufacturers and suppliers ensuring interchangeability and compliance
- OEMs and Tier‑1 suppliers validating component tolerances and surface finishes
- Quality engineers and test labs performing dimensional and force verification
- Aftermarket and remanufacturing operations matching replacement ring specifications
Practical benefits:
- Ensures consistent oil control performance and reduced oil consumption
- Facilitates interchangeability across suppliers and engine platforms
- Provides clear bases for specifying plating, spring forces and drainage features
Related standards
- ISO 6621‑1 (Piston rings - Vocabulary)
- ISO 6621‑4 (Piston rings - General specifications)
- Other parts of the ISO 6626 series and the broader ISO 6621–6627 piston ring family
For designers and manufacturers working with cast iron coil‑spring oil control rings, ISO 6626‑1:2024 is a primary reference for dimensional conformity, spring specification, plating requirements and oil drainage design.