An intercomparison of roundness measurements between ten European national standards laboratories – A. Sacconi, W. Pasin

Abstract
An intercomparison of high-accuracy roundness measurements has been carried out with the participation of the
national standards laboratories of ten European countries. The circulated artefacts were a hemispherical glass standard
and a steel disc. A total of eight roundness profiles were examined, two on the hemisphere and six on the disc. The
eccentricity between external and internal surfaces of the disc was determined, and the effect of various measuring
conditions evaluated. While the overall results show a satisfying agreement for almost all laboratories, room for
further improvements still exists. The uncertainty limit was mainly due to the spindle errors of the roundness
instruments used in each laboratory. These instruments were proven to be of a good quality at the 0.1 pm level.
Below this limit, best results were reported by those laboratories where error separation techniques were available.