FIELD GUIDE / LINKREADY

Check dimensional tolerances and borderline inspection readings

Write explicit size limits, check measurement conditions, and use an assumed reading near the upper limit to understand the role of uncertainty.

By LinkReady · Updated 2026-10-23

Start with a complete requirement

Record the drawing and revision, measured feature, nominal size, deviations, and units. For a tolerance designation, look up the applicable standard and size interval before writing explicit limits. A similar size, old drawing, or standalone table is not a substitute for the current requirement.

Tolerance Master can assist with table values, limits, and units. Measurements and acceptance decisions belong in the actual inspection process.

Check the measurement conditions

Select equipment suited to the feature and required measurement capability; check calibration status and zero.
Clean the surfaces, check burrs, contact, and alignment, and establish the specified conditions for part and instrument.
Measure at the locations and directions required by the drawing and inspection procedure. Multiple locations may be needed to avoid hiding form variation.
Keep original readings and units, and apply the agreed decision rule with measurement uncertainty.

Display resolution is neither measurement accuracy nor the complete uncertainty.

An assumed borderline result

Assume limits of 24.975–24.990 mm, a measured value of 24.989 mm, and expanded uncertainty U = 0.003 mm with coverage information supplied by the inspection provider. These are teaching assumptions.

Illustrative measurement interval: 24.989 ± 0.003 mm

That is 24.986–24.992 mm, crossing the 24.990 mm upper limit.

The reading lies inside the limits, but the interval crosses a boundary. Ignoring uncertainty does not establish conformity with the same confidence. This illustration is not a complete ISO decision-rule implementation or a scrap decision. Apply the agreed rule; improve measurement capability or remeasure when appropriate.

Make the decision traceable

Retain instrument identification, conditions, measurement positions, readings, limits, decision rule, and conclusion. Before arguing about the last digit, compare drawing revision, units, temperature, and method. If assembly matters, check the actual hole–shaft difference and fit requirements as well as each part’s individual limits.

Review deviation-to-limit calculations and the fit-range examples to distinguish lookup from inspection.

Inspection references

The official ISO 14253-1 description covers conformity decisions considering measurement uncertainty. NPL’s Fundamental Good Practice in Dimensional Metrology discusses practical measurement. Apply the relevant drawing, standards, and inspection agreement; this tutorial does not cover every geometric tolerance or a full uncertainty evaluation.