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Consider two Rockwell hardness machines, perhaps a supplier’s machine
and a customer’s machine. Suppose both machines pass indirect verifications.
Will the two machines then measure the same hardness value for a sample
of material. In practice, there is a good chance there will be a measurable
difference in hardness values. It is even possible there could be a significant
difference, with one machine indicating that the material is within specification
tolerances and the second machine indicating the material to be out of
tolerances. Valid determinations of each machine’s measurement uncertainty
(see 8.3) should account for this discrepancy. The simple problem may be that
the uncertainties of the measurements are too large to make valid comparisons.
In this section, recommendations will be made for reducing these types of
measurement differences.
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