For testing boreholes and grooves use pluggauges. For flat test surfaces, special interfacial gauges are used.
There are different shaped measuring surfaces, such as cylinder, sphere, hexagon or square or threaded.
The minimum gauge is measured with the good side. For this, it must be pushed with slight pressure into the hole or groove, while the scrap side may only beak.
New pluggauges usually have a wear interference on the good side, which is why the printed value “0” does not match the actual value.
Example: The good side of a new pluggauge 8 H7 has a dimension of 8.0027 mm, but the tolerance is defined from 8.000 to 8.0129.
However, this wear interference can only be found on the good side.