Durometers

A durometer (aka hardness tester) is a precision instrument and a type of hardness gauge designed to measure the indentation hardness, or Shore hardness, of non-metallic materials. This parameter is critical for quality control and material specification, quantifying a material's resistance to permanent indentation under a specific load.

The non-destructive measurement provides a standardised value essential for ensuring materials meet the performance requirements of their industrial applications. Durometers are indispensable for engineers and technicians working with polymers and elastomers to verify material consistency and predict performance characteristics like durability and abrasion resistance.

Types of Durometers

The choice of durometer is dictated by the material under assessment, with different models calibrated to distinct Shore hardness scales. Each scale uses a specific indenter shape and spring force to ensure accurate measurements for a given class of materials. The most common industrial scales are Shore A, Shore D, and Shore OO, each covering a different range of material hardness.

Shore A Durometers

The Shore A scale measures the hardness of flexible materials like elastomers, rubbers, neoprene, and silicone. Featuring a truncated 35-degree cone indenter, this is the most common scale for assessing materials used in seals, gaskets, and flexible tubing, where pliability is a critical performance attribute.

Shore D Durometers

For harder materials, the Shore D scale is used. It is appropriate for hard rubbers, thermoplastics, epoxies, and rigid plastics. Shore D hardness testers use a sharper, 30-degree cone indenter and a higher spring force to penetrate these resistant surfaces, making it ideal for qualifying materials for pipes and structural plastic components.

Shore OO Durometers

The Shore OO scale is reserved for extremely soft materials, such as sponge rubber, soft gels, and foam. This durometer uses a larger diameter spherical indenter and a very light spring force to prevent puncturing the material, ensuring an accurate reading of its minimal resistance to indentation.

Digital vs Analog

The core difference between digital and analog durometers is their display, precision, and data handling. Digital durometers provide a direct numerical readout that eliminates the parallax error common with analog dials. They typically offer higher accuracy and features like peak hold and data output for statistical process control (SPC). Analog durometers are robust and power-independent but rely on operator skill for accurate interpretation of the needle's position.

How Durometers Work

A durometer's function is based on indentation hardness testing, adhering to standards like ASTM D2240. The device applies a calibrated spring force through a standardised indenter onto the material's surface. The depth of the resulting penetration is measured and is inversely proportional to the material's hardness. A reading of 100 signifies zero penetration (maximum hardness), while 0 indicates maximum penetration. For valid results, the material sample must have a minimum thickness, typically 6 mm, to prevent the substrate from affecting the reading.

Benefits of Using Durometers

Durometers are vital for material characterisation, offering accuracy, repeatability, and ease of use in industrial quality control. Their design is focused on providing clear, standardised hardness measurements.

Durometers Scale Range From 0–100

The standardised 0-to-100 range on each Shore scale simplifies material specifications on technical drawings and quality control documents. This ensures clear communication of hardness requirements between suppliers, engineers, and QA teams.

Analog or Digital Readings

The choice between analog and digital models allows selection based on application needs. Digital models offer superior precision for rigorous quality systems, while analog versions provide a cost-effective, reliable solution for field or workshop checks.

Choice of Shore Hardness Scales

The specialisation of durometers into different Shore scales (A, D, OO, etc.) ensures that a suitable instrument exists for nearly any polymer or elastomer, enabling precise measurement from soft gels to rigid plastics.

Easy to Operate

Durometers are designed for simple operation. The operator places the presser foot flat on the material and applies firm pressure. The hardness value is displayed instantly, requiring minimal training to achieve consistent results.

Applications of Durometers

Durometers are essential in industries where material hardness is a critical performance metric, ensuring product quality and adherence to design specifications.

Manufacturing and Quality Control

In manufacturing, durometers are used for incoming material inspection and final product verification, ensuring that rubber and plastic components like O-rings and hoses meet hardness specifications.

Automotive Industry

The automotive sector uses durometers to test components like tyres, belts, and interior mouldings. Hardness is key to the durability, safety, and comfort of these parts, making durometer testing vital for quality assurance.

Aerospace and Defence

In aerospace, durometers verify the hardness of seals and gaskets in critical hydraulic and environmental systems, ensuring they provide reliable performance under extreme conditions.

Medical Device Manufacturing

For medical devices, material hardness affects function and patient comfort. Durometers test materials for tubing, catheters, and prosthetics to ensure they have the correct physical properties for clinical use.

How to Choose the Right Durometer

Selecting the correct durometer requires evaluating the application's technical needs to avoid inaccurate measurements.

First, identify the material to determine the right Shore scale (e.g., Shore A for elastomers, Shore D for rigid plastics).

Second, assess accuracy requirements; digital models are better for high-precision tasks and data logging.

Finally, consider the frequency of use and budget, which will guide the choice between a feature-rich digital instrument and a practical analog model.

The Leading Supplier and Distributor of Durometers in Hong Kong

RS is your trusted source for professional-grade durometers in Hong Kong. We offer a comprehensive selection from leading manufacturers like Kern, Sauter, and our own RS PRO line. Our range covers multiple Shore scales and includes both digital and analog models at competitive prices, ensuring you can select the ideal durometer for your specific material testing application.

To complement your quality control processes, we also supply a wide array of other testing and measurement instruments, including micrometers, force gauges, and calipers. Purchase your Shore A durometer, Shore D durometer, rubber hardness tester, plastic hardness tester and related accessories online with us today. For complete information on our ordering procedures, delivery options, and associated fees, please visit our dedicated delivery information page.