How does a Rockwell hardness tester differ from a Brinell hardness tester?

The primary difference between the Brinell hardness test and the Rockwell hardness tester lies in how they measure and indicate material hardness.12

Measurement Methodology

• Brinell Hardness Test: This method involves forcing a hardened steel or carbide ball of a known diameter into a material's surface under a specific load. Hardness is determined by measuring the diameter of the resulting indentation using a microscope. The hardness number is then calculated by dividing the load by the spherical area of the indentation.12
• Rockwell Hardness Tester: This device provides a direct reading of hardness. Instead of measuring the size of an indentation after the load is removed, the tester uses a sensitive gauge to measure the depth of penetration of an indenter (a steel ball or a conical diamond known as a brale) under a known load. This depth is measured relative to a minor initial load, and the corresponding hardness value is displayed directly on a dial.12

While the Brinell test is often used for its correlation with ultimate tensile stress, the Rockwell system is widely favored in manufacturing for quality control due to its speed and direct-readout capability.2