What is the difference between Roundness and circularity?

Answer 1

The term roundness and circularity are oftenly used interchangeably. Roundnessis defined as a condition of a surface of revolution (like cylinder, core or sphere) where all points of the surface intersected by any plane perpendicular to a common axis in case of cylinder and core (or passing through a common centre in case of sphere) are equidistant from the axis (or centre). Since the axis and centre do not exist physically, measurement have to be made with reference to surface of the figures of revolution is the circular contour. It may be understood that roundness expresses a particular geometric form of a body of revolution in all the three dimensions, the circular contouris the characteristics form of the entire periphery of a plane figure. For measuringroundness, it is only the circularity of the contour which is determined.