The ten-to-one rule says a measuring instrument's resolution, its smallest readable step, should be no more than a tenth of the tolerance or process spread. A caliper reading to 0.01 mm suits a tolerance band of 0.1 mm or wider, not one of 0.02 mm. The rule is a quick screen for discrimination only; a gauge that passes it can still fail on repeatability, bias or reproducibility.
Tolerance is plus or minus 5 microns and the indicator reads to 2. That breaks the ten-to-one rule before we even start the R&R.
Also heard as
- 10 to 1 rule
- rule of ten
Related terms
P/T ratio
Precision-to-tolerance ratio: measurement system spread as a fraction of the specification width.
Gauge R&R
Study that measures how much observed variation comes from the measurement system's repeatability and reproducibility.
MSA
Measurement systems analysis: the set of studies that prove a gauge is fit for the decisions its data will drive.