4 Types of Durometer Scales

When specifying materials for your engineering designs, understanding the hardness of candidate materials is critical. To compare material hardness in a standardised way, engineers use measurements called durometer values. There are in fact numerous durometer scales, each designed to test materials of a certain hardness range.

In this article, we will explore the 4 most common durometer scales used in engineering today. Learning when to apply each scale will empower you to select optimal materials to meet your functional requirements. With this knowledge, you can confidently specify materials hardened to the ideal degree.

What is a durometer?

A durometer is a device used to measure the hardness of a material. It applies a standardised measurement scale that determines a material’s resistance to indentation. 

How Durometers Work

A durometer has a spring-loaded indenter that is pressed into the material being tested. The further the indenter penetrates the material, the lower its hardness reading. Durometers allow for quick hardness checks without damaging the material. They are a useful quality control tool to ensure materials meet specifications.

Why use a durometer to measure hardness?

To accurately design parts and products, you need to understand the properties of the materials used. One of the most important properties is hardness, which refers to a material’s ability to resist deformation. 

Durability

For parts that experience heavy wear or contact, a harder material may be needed to prevent damage. Softer materials are more prone to scratching, denting or tearing. Knowing a material’s durometer reading helps determine if it can withstand certain environmental conditions or physical stresses.

Suitability

A material that is too hard may damage mating parts, while one that is too soft will not function properly. For example, seals and gaskets require a specific durometer to create an effective seal without causing damage.

Quality

Consistent hardness is important for quality and performance. Measuring durometer at various stages of production helps ensure uniformity and detects any defects. Changes in hardness can indicate problems with the material composition or manufacturing process. Maintaining tight tolerances for durometer optimises the functionality, fit and reliability of parts.

In summary, durometer measurements provide critical information about a material’s hardness and suitability for different applications. By understanding durometer scales and testing materials, you can make better choices when designing high-quality parts and products. The ability to measure, monitor and control hardness is key to success.

What are the types of durometer scales?

There are several types of durometer scales used to measure the hardness of materials. The scale selected depends on the hardness of the material being tested. The most common types are the Shore, Rockwell, Brinell, and Vickers scales.

Shore Scales

The Shore scale is commonly used to measure the hardness of elastomers, plastics and rubbers. The Shore A scale measures soft materials, while the Shore D scale measures hard materials. The Shore M scale measures medium-hard plastics and rubbers. These scales use a durometer indenter to measure hardness.

Rockwell Scales

The Rockwell scale is suitable for measuring the hardness of metals, hard plastics and other rigid materials. The Rockwell C (HRC) scale measures hard materials like steel, while the Rockwell B (HRB) scale measures softer materials like aluminium or brass. These scales measure the depth of indentation left by a diamond cone or hardened steel ball indenter.

Brinell Scale

The Brinell scale uses a 10mm hardened steel ball to indent the material. It is suitable for measuring the hardness of rigid and coarse-grained materials like castings or forgings. The Brinell hardness number (HB) is calculated from the diameter of the indentation. This scale can measure a wide range of materials from soft aluminium to hard steel.

Vickers Scale

The Vickers scale uses a diamond pyramid indenter to measure the hardness of thin sheets and small or thin parts. The Vickers hardness number (HV) is determined from the surface area of the indentation. This scale can measure a wide range of materials, from soft lead to hard steel and ceramics. The Vickers scale provides high resolution and accuracy for very hard materials.

In summary, the type of durometer scale selected depends on the hardness of the material as well as other factors like thickness, grain structure and geometry. The appropriate scale will provide an accurate measurement of the material’s hardness.

Conclusion

In conclusion, understanding the various durometer scales and selecting the appropriate one for your application is critical when measuring material hardness. With 12 main durometer scales to choose from based on your specific material and hardness range, following standard test methods will ensure accurate, repeatable results. 

Proper hardness testing will enable you to validate material specifications and make informed decisions when designing components and products. By selecting the proper durometer scale, you can avoid failures related to incorrect material selection. With this knowledge, you are now equipped to measure a wide range of materials to international standards.