International Rubber Hardness Scale

The shore a scale is used for softer rubbers while the shore d scale is commonly used for harder ones.

International rubber hardness scale. The differential indentation depth is measured and tabulated to read directly in irhd degrees. 30 shore a is much softer than 80 shore a. The hardness is measured by the depth of indentation caused by a rigid ball under a spring load or dead load the indentation being converted to hardness degrees on a scale ranging from 0 to 100. When comparing two materials shore hardness offers a reference point and there are 12 different scales that are used for measuring a range of substances.

A rubber durometer of shore 70a is the most commonly chosen material hardness for all applications. Thus if you need a rubber or o ring durometer that feels like a running shoe sole review our rubber hardness chart below then pick shore 70a. In europe the iso 48 standard and the irhd unit are often used to determine hardness. There are other shore hardness scales such as shore o and shore h but they are rare within the plastics and rubber industry.

The standard test method conducted involves pressing a piece of rubber with a known force for a given time and measure how much the rubber indents in that time. The main advantage of the irhd m method is that the hardness of the rubber can also be measured on the end. If it does not penetrate at all then the durometer is 100 for that scale. The hardness of seal materials such as rubbers plastics and elastomers are measured in units of shore or irhd international rubber hardness degrees.

The spring loaded meter gives shore a values. The readings range from 30 to 95 points. Hardness is one of the most widely measured properties used to characterise rubber. Generally most rubber materials fall under the rubber durometer scale of shore a.

The irhd m micro is mainly used where the test material has a standard thickness of 2 mm. The irhd international rubber hardness degrees instrument has a spherical indentor which indents the sample under a minor and major load. The measurement is made by indenting a rigid ball into the rubber specimen. The international rubber hardness degrees irhd scale has a range of 0 to 100 corresponding to the elastic modulus of 0 0 and infinite 100 respectively.

If the indenter penetrates 2 54 mm 0 100 inch or more into the material the durometer is 0 for that scale. A number of instrument types exist for both the irhd micro dead load and shore a scales are most commonly used for rubber. The irhd international rubber hardness degree scale and the shore scale are widely used. The shore a scale is the most prevalent in the united states.

The final value of the hardness depends on the depth of the indenter after it has been applied for 15 seconds on the material. The reading from a dead load hardness meter is called international rubber hardness degrees irhd.