What should a bearing-bore measurement report state beyond the measured diameter?

LILY Bearing | 2026-10-28

Best answer

A measurement needs a defined meaning

Bearing tolerance tables distinguish different dimensional and running characteristics, and the measurement method determines what a reported value represents.

An isolated diameter with no instrument, measurement location or temperature condition may not be comparable with the specified requirement. JTEKT provides a separate tolerance-measurement section for this reason. The inspection record should state which characteristic was measured and how it was obtained. It should also identify the applicable drawing or tolerance reference. A displayed instrument resolution is not the same as measurement uncertainty, and a nominal size is not an acceptance interval. Keep those concepts distinct when reporting a result.

Write a report another inspector can interpret

Record the complete bearing identity, instrument identification and calibration status, measuring setup, environmental or stabilisation conditions, sampled positions, raw readings and the relevant acceptance reference.

If the measurement cannot support a required tolerance because of instrument capability or missing conditions, state that limitation. For example, “approximately 25 mm by caliper” may help identify a nominal size, but should not become a micrometre-level conformity statement. Preserve the original readings rather than replacing them with an unexplained average. The report then shows both the observed dimension and the strength of the evidence available for deciding whether the specified bore requirement was met.