Engineering Reference

Gauge R&R

A study separating measurement variation into repeatability and reproducibility.

Definition

Repeatability is variation when one operator measures the same part twice; reproducibility is variation between operators. Together they estimate how much of the observed spread is measurement noise rather than real part variation.

The rule of thumb is that measurement variation should be under 10% of the tolerance to be acceptable and under 30% to be marginal. Above that, the gauge is not capable of judging the part, regardless of how precise it appears.

Common misuse

Using a gauge without knowing its R&R. A gauge that consumes half the tolerance makes conforming parts look out of specification.

Related