About Harboro Rubber Engineering in Rubber      Contents      Introduction      Uses of Rubber      Processing Rubber      Designing With Rubber      Selecting / Specifying Rubber          Where Do I Start?          Material Selection          Basic Mechanical              Hardness              Typical Tensile Strengths              Tensile Strengths Table              Compression Set              Compression Set Values          Other Mechanical Properties          Electrical Properties          ASTM and BS Framework          Data Chart      Quality In Rubber      Rubber Directory      Health & Safety      Measuring Properties      Glossary of Terms      Request A Copy Contact Information

Hardness   Once a rubber type has been selected, the hardness range must be determined. Hardness is measured in degrees on the Shore "A" or IRHD scale (the values are similar although Shore "A" readings are usually one to three degrees higher than IRHD readings). Hardnesses are normally based on a nominal figure e.g. 50 ±5° or as a hardness range e.g. 50-60°. Materials below 30° are extremely soft and comparable with foams. These are available but must be regarded as a special requirement. A set of hardness test pieces may be obtained from Harboro on request but the hardness ranges may generally be described as follows: VERY SOFT 30-40° SOFT 40-50° SOFT - MEDIUM 50-60° MEDIUM 60-70° FIRM 70-80° HARD 80-90° VERY HARD 90-100°