ISO 18669-2:2020

Overview

ISO 18669-2:2020, "Internal combustion engines - Piston pins - Part 2: Inspection measuring principles", defines standardized measuring principles for piston pins with a nominal outer diameter from 8 mm to 100 mm. Intended for reciprocating internal combustion engines (road vehicles and other applications), the document specifies how to measure geometric form, dimensions, surface condition and material-related properties to ensure interchangeability, performance and quality control. In non-road applications, the principles can be adapted by mutual agreement between purchaser and manufacturer.

Key topics and technical requirements

The standard sets out measurement principles and general conditions for piston pin inspection, including:

• General measuring conditions
  • Instruments with resolution ≤ 10% of the tolerance.
  • Measurement uncertainty per the ISO 14253 series.
  • Measurement systems analysis (AIAG / IATF 16949) recommended.
  • Reference temperature for OD measurements: 20 °C ± 1 °C.
  • Principle of independence per ISO 8015.
• Outside diameter (d1)
  • Reference method: precision caliper with spherical probes (radius 1.5 mm minimum), applied force ≈ 1 N.
  • Measurement uncertainty example: ±0.0005 mm (per ISO 14253 series).
• Form and runout
  • Cylindricity and circularity measured via polar/macro-form diagrams (reference circle: least squares - LSCY/LSCI).
  • Stylus tip radius: 1.0 mm. Undulations per revolution (UPR): 1–50.
  • Circumferential waviness analysis options: sector roundness (DFTC), filtered bandwidth (band-pass e.g. 10–50 UPR), dominant waviness.
• Other geometrical and dimensional features
  • Edge drop-off, inside diameter(s), concentricity ID→OD, length, gauge length, runout of end faces, end-face concavity/step, end face diameter, outside-edge profile, inside chamfer, tapered bore features.
• Surface and material checks
  • Surface roughness (ISO 4287/4288), case depth (ISO 18203), core and peripheral hardness (Brinell/Vickers/Rockwell standards), non-destructive tests (eddy current, magnetic particle, ultrasonic) and checks for volume change, grinder burn, residual magnetism and visual defects.

Practical applications

• Establishes inspection routines for incoming piston-pin supplies, in-process control and final inspection for engine assembly.
• Ensures dimensional interchangeability and bearing performance in connecting-rod/piston assemblies.
• Supports quality assurance programs in OEMs, tier suppliers and independent metrology labs.

Who should use this standard

• Engine OEMs and powertrain manufacturers
• Piston-pin and bearing component suppliers
• Quality, metrology and inspection engineers
• Laboratory and NDT teams conducting hardness, surface and defect assessments

Related standards

Normative and referenced documents include ISO 18669-1:2013 (general specifications), ISO 14253 (measurement uncertainty), ISO 8015, ISO 4287/4288, ISO 18203, ISO 6506/6507/6508 (hardness), ISO 9934 (magnetic particle), ISO 15548 (eddy current), ISO 16810 (ultrasonic). These provide complementary procedures for surface texture, hardness and non‑destructive testing.