# Concentricity

Mathematically, concentricity (Latin con = with and cetrum = center) means that several geometric figures share a center. The best-known example is concentric circles, but other shapes can also be concentric to each other. In shape and position tolerances as a subfield of geometric product specifications, concentricity is therefore a position tolerance in the class of location tolerances. Unlike shape tolerances, it therefore does not specify which geometry an object must fulfill, but rather in which position, specifically at which location, an element must ideally be located in relation to a given reference. The concentricity of an object is given if the center of the toleranced circle lies in a circle whose center is concentric to the reference. Thus, the concentricity tolerance is always based on an axis of a rotationally symmetric element. It is thus an essential component of concentricity tolerances. 3D metrology offers a variety of methods to ensure the concentricity of elements. Concentricity measurements can also be used to check concentricity. The representation of concentricity tolerances in technical drawings is regulated by the ISO GPS standards.