Manufactured parts are affected by size and form errors, which need to be assessed
against geometrical and dimensional tolerances in order to meet the functional
requirements they have been conceived for. The compliance assessment of workpieces with
specifications depends on measurements and is unavoidably affected by several uncertainty
contributions. According to the geometrical product specifications and verification (GPS),
measurement uncertainty consists of method and implementation uncertainty. Literature
proposes different approaches for the evaluation of implementation uncertainty, however a
standardized method has not been yet achieved. This paper makes an analysis of the various
elements to be considered when choosing a specific approach: in the implementation
uncertainty of circular features. The most common manufacturing signatures affecting
circular profiles were considered, together with the number of points necessary for a
reliable estimation of implementation uncertainty.