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It is generally not possible to make good Rockwell hardness measurements
with a poorly operating machine. The initial consideration should be to use
a Rockwell machine capable of measuring to the required accuracy and
repeatability. As discussed previously, the errors in the operating components
of the hardness machine should be identified and assessed through the direct
verification process (see 5.1). Depending on the required level of accuracy,
simply meeting the specified operating tolerances may not be adequate.
Adjustments may be needed to bring each component to the center of
tolerance. Unfortunately, for many types of Rockwell hardness machines,
these types of adjustments are not possible in the field and, in many cases,
may not be possible at all.
It is also important to use indenters that have been certified as meeting all of
the requirements specified in the test method standards, including the shape
and alignment. Until recently, obtaining certifications of the physical dimensions
of diamond or ball indenters has been difficult. Once in use, indenters should be
inspected frequently by visual means to help determine if damage has
occurred.
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