Rockwell hardness testing

The Rockwell testing method is one of the most widely used techniques in quality control and material verification. Known for its speed, repeatability and straightforward operation, Rockwell hardness testing is a cornerstone in the production and inspection of metals, plastics and composites.

At GNEHM, we provide high-precision Rockwell hardness testers that comply with international standards and are built for maximum accuracy in both laboratory and production environments. 

Discover how our Rockwell testers can support your process, and request a personalized quote today.

Rockwell hardness testing is used to determine how resistant a material is to permanent surface deformation. It is based on the differential-depth principle and supports a wide range of scales, making it suitable for different materials and hardness levels. This method offers a quick and consistent way to evaluate the hardness of metals, plastics and composite materials, and is widely applied in both manufacturing and quality control environments.

How the Rockwell method works

The Rockwell test measures the permanent depth of an indentation left by an indenter under load. It involves two main steps:

1. A minor load (10 kgf) is applied to position the indenter and eliminate surface irregularities. 
2. A major load (typically 60, 100 or 150 kgf) is then applied and removed, after which the depth of the indentation is measured. 

The hardness value is then calculated and displayed as a Rockwell hardness number, such as HRC for hardened steel, HRB for softer metals like brass or aluminium, or HR15N for thin surface coatings. This makes the Rockwell test a fast and reliable testing method with no need for optical measurement. 

Test load range

The Rockwell method operates within the macro load range, with test forces typically starting at 49.03 N (5 kgf) and going up to 1471 N (150 kgf), depending on the selected scale. For example, HRB uses a test force of 98.07 N (10 kgf), while HRC applies the maximum load of 1471 N (150 kgf). Each scale combines a specific force and indenter type to ensure accurate and application-specific hardness measurements.

Accuracy and testing conditions

To ensure maximum repeatability and accuracy, the Rockwell method requires:

• A minimum sample thickness of at least 10x the indentation depth
• A clean, smooth test surface, free from scale, coatings or oxidation
• Stable temperature and vibration-free testing environments

Automated and semi-automated testers further reduce operator influence, improving consistency across batches.

As part of the Rockwell method, the type of indenter used plays a crucial role in determining accurate results. Rockwell testing machines usually use two main types of indenters:

• Diamond Cone (brale): for harder materials, typically with a 120° cone angle and a polished 0.2 mm radius tip.
• Hard metal balls: made of tungsten carbide, available in multiple diameters (1/16″, 1/8″, 1/4″, 1/2″) for softer materials such as aluminium, copper, and certain plastics.

The correct combination of indenter and scale ensures accurate, application-specific hardness readings.

Rockwell testing is widely used across industries such as:

• Automotive: for components like gears, shafts and springs
• Aerospace: for structural parts and surface-coated materials
• Metalworking: for general quality control of metal parts

It can also be applied to certain plastics and polymers, using superficial Rockwell scales designed for softer materials. Its rapid results and minimal sample preparation make Rockwell ideal for inline and end-of-line inspection.

• Direct digital readout, no microscope needed
• Fast testing cycles, ideal for high-volume production
• Supports a wide range of Rockwell scales for different materials
• Conforms to ISO 6508 and ASTM E18
• Excellent repeatability and minimal user error

Limitations to consider

• Not suitable for very thin materials or layered composites
• Surface roughness or coatings can distort results
• Limited insight into material structure compared to microhardness methods like Vickers and Knoop testing

Our Rockwell hardness testers combine Swiss precision engineering with user-friendly features:

• Closed-loop force control for precise load application
• Touchscreen operation with intuitive test cycle setup
• Automatic test sequences
• Built-in memory for storing results and protocols
• Optional support for Brinell testing methods

Whether you are testing a single sample or performing high-throughput quality control, GNHEM testers deliver reliable results you can trust. View our Rockwell hardness testers on the product page.

Accessories and consumables for Rockwell testing

For accurate and standardised results, GNEHM offers certified reference blocks for regular calibration and verification, indenters for all Rockwell scales and applications and accessories for sample preparation and fixture alignment. All consumables are compliant with ISO and ASTM regulations.

Looking for a high-precision Rockwell hardness testing machine tailored to your materials and production process? Get in touch with our technical experts to discuss your needs. We’ll help you select the right solution for consistent and traceable testing results. Contact us or request a personalized quote today.

Looking for an alternative to Rockwell? Discover our Vickers hardness testers and Brinell hardness testers for different materials an precision needs.