When I worked for Carpenter Technology Corporation in their research center, we encountered several cases where chart ratings of specimens by their production lab yielded grain size ratings between 4 and 5 for a number of specimens on an order (these orders required tests on 20 specimens from different bars). When we re-tested them in the R&D center, we got similar chart ratings. But, when we actually measured the grain size, all ratings were between 5 and 6 on the ASTM E 112 scale. As the criterion for pass/fail was a grain size of 5 or finer (higher), this bias was important. Consequently, at a subsequent ASTM E-4 committee meeting, I conducted a “round robin” test.
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