In measuring the internal diameters (or hole sizes) plug gauges employ the go/no-go principles. These tools for precision inspection made of gauge steel with 60-65 HRC hardness have surface finishes where Ra ≤ 0.2 μm and meet tolerances of H7/g6 for fit checks on bearing housed automotive engine components. Moreover, they also use ring gauges in checking the external diameter or the shaft size range.
