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O-Ring Hardness Chart
O-Ring Hardness Chart
O-ring hardness is a critical factor that affects sealing performance, extrusion resistance, and service life. Hardness is typically measured using the Shore A durometer scale for elastomer O-rings.
What Is O-Ring Hardness?
O-ring hardness refers to the resistance of the elastomer material to indentation. It directly influences how the O-ring deforms under pressure and how well it seals against mating surfaces.
- Measured in Shore A durometer
- Lower values = softer, more flexible
- Higher values = harder, more extrusion resistant
Standard O-Ring Hardness Chart (Shore A)
| Hardness (Shore A) | Typical Characteristics | Common Applications |
|---|---|---|
| 60 Shore A | Very soft, excellent sealing at low pressure | Static seals, low-pressure applications |
| 70 Shore A | Standard hardness, good balance | General hydraulic & pneumatic systems |
| 75 Shore A | Slightly harder, improved extrusion resistance | Dynamic seals, moderate pressure |
| 80 Shore A | High pressure capable | High-pressure hydraulic systems |
| 90 Shore A | Very hard, excellent extrusion resistance | Extreme pressure, backup ring applications |
Recommended Hardness by Application
- Static sealing: 60 – 70 Shore A
- Dynamic sealing: 70 – 80 Shore A
- High-pressure systems: 80 – 90 Shore A
- Vacuum applications: 60 – 70 Shore A
Hardness vs Pressure Resistance
Higher hardness O-rings offer better resistance to extrusion under pressure, but may require higher compression force to achieve an effective seal.
For high-pressure systems, harder O-rings are often used in combination with backup rings to prevent extrusion.
Hardness by Material Type
- NBR (Buna-N) O-Rings: 60 – 90 Shore A
- FKM (Viton®) O-Rings: 70 – 90 Shore A
- EPDM O-Rings: 60 – 80 Shore A
- Silicone O-Rings: 50 – 80 Shore A
- FFKM O-Rings: 70 – 90 Shore A
How to Choose the Right O-Ring Hardness
- Operating pressure
- Static or dynamic application
- Temperature range
- Chemical exposure
- Groove design and tolerances
For guidance on groove dimensions, refer to our O-Ring Groove Design Guide.
Custom Hardness & OEM Support
We offer O-rings in custom hardness, materials, and colors to meet specific application requirements. OEM and bulk supply services are available.