A durometer is a device or an instrument that’s used to measure the hardness of various materials, which is mostly used to measure the hardness of materials such as elastomers and polymers such as plastics and rubber. To do this, durometers rely on standardized measuring methods in which the results are derived from the measurements taken during material testing.

Durometers measure the depth of an indentation made into the material under a standardized force. Softer materials will allow a deeper indentation, while harder materials usually allow shallower indentations.

The hardness of a material is typically taken from the dial or the device’s digital display, which relies on a Shore Hardness scale. There are several different scales, like Shore 00, Shore A scale, and Shore D scale. The values on these scales typically range from 0 to 100, with lower numbers denoting softer materials and higher numbers corresponding to harder ones.

Durometer hardness testing isn’t universal, and there are differences in durometer testing methods based on the type of the tested material, the durometer scale, and the specific standards followed during testing.

The basic principle behind these testing methodologies remains the same, but the exact testing method varies depending on the application. For example, Shore Durometers are the most commonly used for testing hardness and typically rely on one of the aforementioned hardness scales.

The scale selection, which mostly depends on the material, also determines the indentor shape, with Shore A using a truncated cone. Shore D uses a pointed cone, while Shore OO relies on spherical indentations.

The exception to these rules is the IRDH durometers, also known as the international rubber hardness degree durometers, which rely on ball indentors to measure the indentations in rubber. Regardless of the type, nearly all measurements involve pressing the indentor into the material for 15 seconds and then reading the hardness value.

However, some measurements involve shorter durations, with pressure time lasting as short as three seconds. These measurements are mostly used for materials that quickly change shape under pressure, such as gels and soft rubbers.

It’s important to note that all testing methods have to be conducted in adherence to corresponding standards, ensuring the adequacy of measuring methods. Standards such as ASTM D2240, ISO 7619-1, and DIN 53505 provide specific guidelines for sample preparation, testing environments, and equipment calibration.

Choosing the correct durometer method depends on the type of material used since the material dictated the hardness scale used during testing. The main difference between Shore A and Shore D hardness scales lies in the fact that Shore A hardness scale is typically used to measure more flexible rubbers and soft materials, while Shore D is used for harder and more rigid materials.

It’s important to know that these scales aren’t interchangeable. For example, a rubber band is 60 00 on the Shore 00 scale and only around 20A on the Shore A scale. Likewise, tire treads sit around 96 00 on Shore 00, 70A on Shore A, and 30D on Shore D hardness scale. Shopping cart wheel hardness can’t be measured using Shore 00, but they measure 100A and 60D on the other two scales.

The use of a durometer, as well as the aforementioned scales, plays a role in determining the material’s resilience. For example, suppose you’re looking for a material that needs to grip a particular surface but also withstand sliding abrasion. In that case, you’re more likely to find such materials at the harder end of the Shore A scale.

Likewise, if you’re looking to decrease friction coefficient, the materials on the Shore D scale will generally produce less drag and, thus, less grip. However, if you go too high on the Shore D scale, the materials become very hard but also very brittle; think of hard hats.

During the beginning stages of project development, engineers and product development teams dedicate a good portion of their time to understanding their products’s end-use applications and the project requirements. The considered factors help narrow the selection of potential materials to those capable of fulfilling the desired specs.

Understanding the mechanical specifications of these prospective materials, including physical, chemical, and mechanical properties, is rather important, as it helps determine how the material performs under certain conditions and how durable it is. One of the most important factors for engineers and product development teams is material hardness.

The hardness of different materials refers to their respective resistance to being permanently indented or penetrated. This is where durometer hardness measures come into play. If the manufactured product has to support a lot of weight over a longer period of time, the development teams should look to the shore hardness scales.

For parts that need to withstand weight for long, development teams can safely neglect the entire Shore 00 scale and consider materials ranging from 70A on the Shore A scale to 60D on Shore D scale.

Engineers often have to balance materials specifications, especially when it comes to plastics or metals. Harder plastics are very brittle and prone to breaking during machining, while harder metals might be too expensive or difficult to machine.

To work around these difficulties, engineers often employ post-process hardening treatments to achieve higher hardness while maintaining the ease of processing and machining. Ultimately, durometer hardness isn’t the only defining factor when it comes to material properties, and it shouldn’t be mistaken for material strength or corrosion resistance.

It’s important for engineers and product developers to select the best material for their specific requirements. Besides hardness, this also includes other mechanical properties, which are too many to count for this particular guide.

Durometers are devices that are used to measure the hardness of materials, such as rubber or plastic, by comparing the reading values to previously established reference points across three different scales. If you want to learn more about material hardness, don’t hesitate to contact Reid Supply, and check out the company’s extensive download library.