In rubber part design, hardness (durometer) value is one of the fundamental parameters that determines how a product behaves in its application. Choosing the right hardness directly affects factors such as sealing performance, wear resistance, and ease of assembly.
The Shore A and Shore D Scales
The most commonly used scale for rubber and soft elastomers is Shore A, measured on a 0-100 scale. For very hard, plastic-like materials, the Shore D scale is used. General sealing gaskets are typically produced in the 50-80 Shore A range.
Factors Affecting Hardness Selection
- Sealing requirements (lower hardness conforms better)
- Mechanical load and pressure
- Assembly method (compression, press-fit, etc.)
- Vibration damping needs
- Wear and abrasion resistance
Risks of Choosing Too Soft or Too Hard
A rubber that is too soft may be more prone to permanent deformation or wear under mechanical load. A rubber that is too hard may fail to conform to surface irregularities, reducing sealing performance. The right balance should be determined based on the application’s actual conditions.
A Practical Recommendation
For a new design, starting from hardness values used in similar existing applications and validating the final choice with a sample test is the most reliable approach.
Alpin Rubber offers customers application-specific solutions with the capacity to manufacture across a range of hardness values.