Overview
ISO 18669-2:2025 - "Internal combustion engines - Piston pins - Part 2: Inspection measuring principles" defines the measurement principles used to inspect piston pins for reciprocating internal combustion engines. It applies to piston pins with a nominal outer diameter (OD) from 8 mm to 100 mm and is intended for road-vehicle engines and other applications (with agreed modifications where appropriate). The standard complements ISO 18669-1 (general specifications) and aligns inspection methods with GPS and NDT practices.
Key topics and technical requirements
- Scope and applicability: Measurement rules for piston pins (OD 8–100 mm); adaptable for non-road applications with purchaser/manufacturer agreement.
- General measuring conditions:
- Instrument resolution ≤ 10% of the tolerance of the measured dimension.
- Measurement uncertainty to follow ISO 14253 series.
- Measurement systems analysis reference: AIAG / IATF 16949.
- Reference temperature for OD: 20 °C ± 1 °C.
- Apply the principle of independence per ISO 8015.
- Outside diameter (OD):
- Reference method: precision caliper with spherical probes (radius 1.0 mm) applying ~1 N force.
- Stated measurement uncertainty: ±0.0005 mm (per ISO 14253).
- Form and surface characteristics:
- Cylindricity: Multiple polar diagrams per ISO 12180-2 (least-squares reference cylinder, Gaussian filter, stylus tip radius 1.0 mm, UPR 1–50).
- Circularity: Polar macro-form per ISO 12181-2 with similar parameters.
- Circumferential waviness, edge drop-off, concentricity (ID vs OD), runout, end-face features, surface roughness, case depth, hardness and material defects are defined with measurement principles or referenced test methods.
- NDT and hardness references: Links to ISO 9934 (magnetic particle), ISO 15548 (eddy current), ISO 16810 (ultrasonic), and hardness standards (ISO 6506/6507/6508).
Applications and users
ISO 18669-2:2025 is used by:
- OEMs and engine builders for production and incoming inspection of piston pins.
- Tier-1/2 suppliers manufacturing pins and components for internal combustion engines.
- Metrology laboratories and quality-engineering teams implementing inspection measuring principles, measurement uncertainty and measurement systems analysis.
- NDT and failure-analysis teams assessing material defects, case depth and grinder burn.
Typical uses: production quality control, supplier agreements, design validation, R&D and root-cause analysis.
Related standards
Keywords: ISO 18669-2:2025, piston pins, inspection measuring principles, internal combustion engines, outside diameter, cylindricity, circularity, measurement uncertainty, GPS.