O-Ring Tolerance Standard Table
O-rings are widely used for sealing applications in hydraulic, pneumatic, and mechanical systems. To ensure optimal sealing performance, correct dimensional tolerance control is essential. This article summarizes international tolerance standards (DIN3771), commonly used for O-ring Inside Diameter (ID) and Cross Section (CS) dimensions.
🔍 Why O-Ring Tolerances Matter
Prevent leakage and over-compression
Ensure proper squeeze and stretch ratio
Increase sealing reliability and lifespan
Meet OEM or industry compliance (FDA, ISO, etc.)
📏 DIN3771 – Tolerance Table
Cross Section (CS) Tolerance
| Nominal CS (mm) | Tolerance ± (mm) |
|---|---|
| 0-1.8 | 0.08 |
| 1.81-2.65 | 0.09 |
| 2.66-3.55 | 0.10 |
| 3.56-5.3 | 0.13 |
| 5.31-7 | 0.15 |
| 7.01-8.7 | 0.18 |
| 8.71-10.4 | 0.22 |
📐 Common O-Ring Standards
| Standard | Region | Notes |
|---|---|---|
| AS568 | USA | Imperial sizing, widely adopted |
| ISO 3601 | Global | Metric & inch available |
| JIS B2401 | Japan | Preferred in Asian industries |
| DIN 3771 | Europe | Used in machinery and hydraulics |
🧰 How to Measure O-Ring Dimensions
Use a digital caliper to measure ID and CS
Compare actual values with standard tolerances
Check material shrinkage from molding process
Request manufacturer certificate or inspection report
🏭 CNL O-Ring Quality Control
Full compliance with DIN3771
Size range: ID 1 mm to 670 mm; CS 1.0 mm to 10.0 mm
Available materials: NBR, FKM (Viton), EPDM, Silicone, HNBR
ISO Class A / Class B / Custom tolerance options
Certification: RoHS, REACH, FDA available