Geometric qualification of standard rings and plugs

5 f.: il.This work aims to demonstrate the metrological capability of the Dimensional Metrology Laboratory of the National Institute of Metrology, Standardization and Industrial Quality (INMETRO) in the calibration of internal and external diameter standards. Reference systems are used to measure roundness, diameters, straightness of generators, squareness between a reference surface and generators and parallelism between generators. The roundness deviation is measured with a special form measuring machine, achieving a very small measurement uncertainty. The other features are measured with a system composed by a co-ordinate measuring machine (CMM) and a linear laser interferometer adapted to it. Some technical considerations and cares that have to be taken when carrying out measurements aiming more accurate results are presented, as well as measurement results of a standard ring and a comparison between our laboratory and the “Physikalisch- Technische Bundesanstalt “ (PTB - Germany)