Rationale

Current wording (§5.3): "External surfaces of weights shall have a surface roughness average of 3.2?µm or less as specified in ASME B46.1." Proposed wording (§5.3): "External surfaces of weights should have a maximum surface finish (Roughness Average or Ra) of 3.2?µm (125?µin.)” Rationale: The 3.2 µm maximum in §5.3 functions as a design recommendation, not as a calibration acceptance criterion. ASME B46.1 specifies the measurement method, and the 3.2 µm value is itself a maximum, so the requirement is technically verifiable. The substantive issue is that the standard assigns no contribution from surface finish to the measurement uncertainty budget and provides no acceptance procedure linking surface finish to calibration validity. Auditors have cited laboratories for non-compliance against a requirement that the standard itself does not define how to verify. ISO 376 contains no equivalent requirement. In informal polling of peer laboratories, none have produced documented compliance records; several believed they were compliant but could not produce evidence on request. Changing the verb from shall to should aligns the requirement with its actual function as a recommended design criterion. The parenthetical “(125?µin.)” is retained as informational only, consistent with the SI-only convention of E2428 and with the analogous E74 ballot. Adding the verification clause provides two practical methods: a comparator block as the rigorous option, and a standard machinist’s fingernail check as the no-equipment fallback, so that a laboratory can demonstrate compliance using techniques already in use at incoming inspection across the industry.