We conclude our discussion of hardness testing by offering some final thoughts.

Most people need not be experts in all the intricate details of hardness testing. However, it is important that the user selects the appropriate hardness-testing method and scale, consider part geometry and test location, and be aware of equipment limitations. Failure to do so can lead to improper interpretations of the true material condition, properties and hardness.

Should you find yourself in a dispute regarding hardness and hardness-testing methods, the first item to confirm is that the specified hardness is appropriate for that material. Next, investigate how the hardness was measured and if it is an appropriate method for that sample. While there can be shades of gray and varying levels of uncertainty between hardness-testing machines or laboratories, expect some level of consensus if the methods are correct.

Everyone involved with hardness testing should be familiar with the appropriate ASTM specifications, including E3, E10, E18, E103, E140 and E384 (and others as necessary). These specifications address proper sample preparations, selection of loads and penetrators, sample geometry, minimum sample thickness considerations, roundness corrections, spacing and edge considerations, and conversions between scales.