Metal hardness is measured by which scale?

The Rockwell Hardness scale is widely used in material science to measure the hardness of metals and other materials. This scale operates on the principle of measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload. The results are quantified in numbers, providing a direct measure of hardness that can be easily interpreted. The Rockwell scale allows for various indentation sizes and loads, making it versatile and applicable for different materials, especially metals.

In contrast, the other scales mentioned serve specific purposes as well. The Mohs Hardness scale is primarily used for minerals and ranks them based on their ability to scratch one another. The Knoop Hardness scale is typically utilized for very brittle materials or thin layers, offering a much smaller indentation which is not always practical for larger metal samples. The Brinell Hardness scale involves creating a larger indentation with a hardened steel or carbide ball, making it more suited for certain applications but less convenient for quick testing compared to the Rockwell method. Thus, the Rockwell Hardness scale stands out for its effectiveness and ease of use in the context of metals.