NF T47-501 O-Ring Standard
French metric O-ring sizes for hydraulic, pneumatic and industrial sealing applications.
NF T47-501 is the French national standard for metric O-ring dimensions, used extensively in France, Belgium, North Africa and francophone markets for hydraulic systems, automotive assemblies, pneumatic equipment and general machinery. The standard is closely aligned with ISO 3601 and DIN 3771, making it interchangeable for most European applications. NF T47-501 specifies inside diameters and cross sections in millimetres, and is frequently referenced in French OEM drawings, public works contracts and aerospace ground equipment specifications.
Cross Sections
| Cross Section (mm) | Notes |
|---|---|
| 1.00 | Precision instruments, small pneumatic fittings |
| 1.50 | Miniature hydraulic and medical devices |
| 1.60 | European small-bore sensors and valves |
| 1.78 | Compatible with AS568 imperial cross section |
| 1.80 | Equivalent to ISO 3601 A-series |
| 2.00 | General purpose static and dynamic seals |
| 2.40 | Medium-pressure hydraulic applications |
| 2.50 | Pumps and fluid handling equipment |
| 2.62 | Compatible with AS568-1xx cross section |
| 2.65 | Equivalent to ISO 3601 B-series |
| 3.00 | Heavy-duty static seals |
| 3.53 | Compatible with AS568-2xx cross section |
| 3.55 | Equivalent to ISO 3601 C-series |
| 4.00 | Large bore flanges, industrial valves |
| 5.00 | High-pressure hydraulic cylinders |
| 5.30 | Equivalent to ISO 3601 D-series |
| 5.33 | Compatible with AS568-3xx cross section |
| 6.00 | Marine and large industrial equipment |
| 6.99 | Compatible with AS568-4xx cross section |
| 7.00 | Equivalent to ISO 3601 E-series |
| 8.00 | Specialised heavy static sealing |
Tolerances
| Cross Section (mm) | CS Tolerance | ID Range | ID Tolerance |
|---|---|---|---|
| 1.00 - 1.60 | ±0.08 | ≤ 10 | ±0.14 |
| 1.00 - 1.60 | ±0.08 | 10 - 20 | ±0.17 |
| 1.78 - 2.65 | ±0.09 | ≤ 13 | ±0.17 |
| 1.78 - 2.65 | ±0.09 | 13 - 30 | ±0.22 |
| 1.78 - 2.65 | ±0.09 | 30 - 50 | ±0.28 |
| 3.00 - 3.55 | ±0.10 | ≤ 20 | ±0.20 |
| 3.00 - 3.55 | ±0.10 | 20 - 40 | ±0.28 |
| 3.00 - 3.55 | ±0.10 | 40 - 85 | ±0.36 |
| 4.00 - 5.33 | ±0.13 | ≤ 40 | ±0.28 |
| 4.00 - 5.33 | ±0.13 | 40 - 80 | ±0.36 |
| 4.00 - 5.33 | ±0.13 | 80 - 140 | ±0.45 |
| 6.00 - 7.00 | ±0.15 | ≤ 80 | ±0.36 |
| 6.00 - 7.00 | ±0.15 | 80 - 160 | ±0.45 |
| 8.00 | ±0.18 | ≤ 120 | ±0.45 |
| 8.00 | ±0.18 | 120 - 250 | ±0.56 |
Common Size Examples
| Inside Diameter (mm) | Cross Section (mm) | Application |
|---|---|---|
| 3.00 | 1.00 | Precision instruments |
| 5.00 | 1.50 | Small pneumatic fittings |
| 7.00 | 1.80 | Compact hydraulic fittings |
| 10.00 | 2.00 | General machinery seals |
| 15.00 | 2.50 | Pump and valve housings |
| 20.00 | 2.65 | Hydraulic cylinders |
| 25.00 | 3.00 | Medium-pressure systems |
| 30.00 | 3.55 | Industrial flange seals |
| 40.00 | 4.00 | Large static seals |
| 50.00 | 5.00 | Heavy equipment hydraulics |
| 80.00 | 5.30 | Large bore hydraulics |
| 100.00 | 6.00 | Marine and offshore |
| 150.00 | 7.00 | Large industrial tanks |
| 200.00 | 8.00 | Specialised static sealing |
Cross Reference to Other Standards
| Standard | Region | Designation Notes |
|---|---|---|
| ISO 3601 | International | A/B/C/D/E series map directly to NF T47-501 dimensions |
| DIN 3771 | Germany/EU | German metric sizes are functionally equivalent to NF T47-501 |
| SMS 1588 | Sweden | Swedish metric sizes share the same cross sections and ID ranges |
| JIS B 2401 | Japan | P/G/S/V series are metric-compatible with NF T47-501 |
| AS568 | USA | Imperial cross sections convert to nearest metric NF sizes |
Groove Design Guidelines
Static Seals
Groove width ≈ 1.15 × CS with 15-25% compression depending on face or radial orientation.
Dynamic Seals
Groove width ≈ 1.2-1.3 × CS. Target 10-15% compression for reciprocating motion to minimise friction.
Rotary Seals
Limit groove fill to 75-80% max. Use harder grades (80-90 Shore A) and materials with good heat resistance such as FKM or HNBR.
NF T47-501 FAQ
Is NF T47-501 the same as ISO 3601?
They are closely aligned but not identical. NF T47-501 is the French national standard, while ISO 3601 is international. Most cross sections and size ranges overlap, making them interchangeable in practice.
What industries use NF T47-501 O-rings?
NF T47-501 is widely used in French automotive, aerospace ground support, agriculture machinery, public works, hydraulics, and marine equipment throughout France, Belgium and North Africa.
Can you supply NF T47-501 O-rings with material certifications?
Yes. We provide batch certificates, material test reports, and full traceability for NBR, FKM, EPDM, HNBR and silicone NF T47-501 O-rings.
Do you stock NF T47-501 sizes or manufacture to order?
We manufacture NF T47-501 O-rings to order with no tooling charge for standard cross sections. Custom sizes and special compounds are available with MOQ starting at 1 piece.
Need NF T47-501 O-rings?
Request a quote for French standard metric O-rings. Custom sizes and fast delivery available.
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