Rockwell hardness testing uses an indenter to apply a minor load and then a larger load; the hardness value is obtained from what?

• A. The difference in depth between the minor and major loads
• B. The diameter of the indent
• C. The color change on the scale
• D. The time of loading

Answer: (A)

Rockwell hardness testing measures how far the indenter penetrates the material under two applied loads. You first put on a small minor load to create a reference indentation, then add a larger major load to increase penetration. When the larger load is removed, the remaining depth of the indentation reflects the material’s resistance to deformation. The hardness value is read from the difference in depth between the minor- and major-load penetrations, not from the indent’s diameter, any color change, or the loading time.