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Close-up of conveyance technician installing v-guides on a red conveyor belt
Helpful Tips to Improve Your V-Guide Knowledge
March 29, 2022
Close-up of conveyance technician installing v-guides on a red conveyor belt
Helpful Tips to Improve Your V-Guide Knowledge
March 29, 2022

Why It's Important to Understand Durometer and Shore Hardness Scales

Why It's Important to Understand Durometer and Shore Hardness Scales

When selecting a material for a new application, one of the most important factors to consider is the material’s hardness. The hardness of a material can severely impact its success in an application. For example, compare the hardness of a shoe insole to that of a shoe heel. While both items are often made of rubber, one is far more durable.

Measuring material hardness can also be beneficial to performing maintenance on your system’s materials. A great example is NASA monitoring the hardness of ship tiles in space to ensure they are ready for re-entry into Earth’s atmosphere.

Generally, material hardness is determined using the Shore hardness scale and the durometer hardness test.

What Is a Durometer?

A durometer is a tool designed to measure the hardness of many non-metallic materials, including rubber, vinyl, polyester, leather, nitrile, and neoprene. This tool resembles a tire pressure gauge, as it is composed of a needle on a spring and a number gauge ranging from 0 to 100.

To estimate a given material’s Shore hardness scale, the durometer’s needle will attempt to penetrate the material. The material’s hardness is determined by measuring its resistance to penetration and any resulting permanent indentation. The pressure of this penetration then activates the gauge on the device, giving a number reading between 0 and 100.

Depending on the gauge’s number reading and the size of the durometer needle used, this result will fall under certain Shore hardness scales.

What Are Shore Hardness Scales?

To understand Shore hardness scales, it’s important to note that a durometer is not a unit of measurement. Rather, a durometer is a dimensionless measurement based on the relative hardness of various materials. Thus, the Shore hardness scale establishes a common reference point for comparing these materials.

Durometer is bucketed into three Shore scales. Each Shore scale ranks in hardness from 0 to 100:

  • 00 – Measures light foams, sponge rubber, and soft gels
  • A – Measures soft rubber, plastics, and rubber-like elastomers
  • D – Measures hard rubber, plastics, and thermoplastics

Each of the three Shore scales uses a durometer with a different-sized needle. Due to this variety in needle size, certain Shore scales are best for measuring certain kinds of material.

Regardless of which Shore scale the measurement falls under, higher numbers mean higher resistance to the durometer needle, while lower numbers show lower resistance. Materials that score lower are softer, while materials that score higher are harder.

The image below depicts various materials and what Shore hardness scales they fall into.

Note: Materials can fall into more than one Shore scale. If the material does fall into more than one scale, the measurement numbers will likely differ from one Shore type to another.

The illustration below shows the difference between a Shore A and a Shore D indenter needle. Due to their difference in size, both needles can produce very different number readings for the same material.

What Material Does My Application Require?

Various industries and applications will require different materials, so it’s important to perform durometer hardness tests before implementation. For example, softer compounds that offer less resistance are ideal for low-pressure seals where the material must conform to rough or uneven surfaces. In contrast, harder materials are more appropriate for high-pressure seals.

Not sure what material your application requires? Reach out to our specialists, who will be happy to help you with the selection process.

Know what materials you need? Request a quote today.

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