Concentricity refers to a center of circular surfaces if the diameter of a cylinder is smaller than its hight.
In this case, for example, the center of a hole must be inside a circle of the specified diameter.
This applies around a reference point in the cross section.
For coaxiality, the axis of a selected diameter must be within a tolerance zone, which is represented by a cylinder of given diameter.
The axis or directional normal must lie on a common reference axis A-B.
The rule that cylinders with diameters greater than their height are tolerated via concentricity serves to distinguish the two terms.
Otherwise, coaxiality is tolerated.
![Concentricity in Plastic Industry Concentricity in Injection Molding](https://www.plexpert.ca/wp-content/uploads/2021/12/Concentricity.png)
Quality Assurance: The axis of the diameter must be within a cylinder of 0.02mm (reference axis A-B)
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