A key distinction between Rockwell testers and the Brinell, Vickers and Knoop testers is that the latter three use optical technology, while Rockwell does not—which generally makes it less costly, makes testing quick and easy, and the surface finish of the specimen is not critical. 

The Vickers and Knoop microhardness testing methods have become invaluable for the testing of a variety of parts, which have what can be referred to as “shallow layer hardness.” Such characteristics as surface hardness, thin cross section, coating hardness, and case depth are measured using the microhardness testing methods. These methods also can be useful for selective testing of particular grains or constituents such as those found in powdered metal parts.

By their nature, microhardness testers are delicate instruments. Extremely light forces must be accurately applied, and the resultant impressions must be precisely measured under high magnification.