Calibration of 1-D CMM artefacts: step gauges (EURAMET.L-K5.2016)

The results of the inter-RMO key comparison EURAMET.L-K5.2016 on the calibration of a step gauge are reported. Twenty-two National Metrology Institutes from four different metrological regions all over the world participated in this comparison which lasted three years, from December 2015 to December 2018. Two artefacts were circulated so that the varying ranges of participants equipment could be accommodated. A 1020 mm ceramic monolithic step gauge remained stable throughout the comparison. A 610 mm steel step gauge changed length, possibly due to an impact while travelling between participants. The comparison of this artefact was divided into two groups, those before the damage and those after, with the reference value for each group derived from a linking participant who had demonstrated equivalence in the 1020 mm artefact circulation. For the 1020 mm comparison the inverse-variance weighted mean was taken as reference value. Of the twenty two participants, eleven successfully demonstrated the validity of the claimed measurement capability. Of the remaining 11, 3 submitted revised uncertainties after the initial circulation of results which were shown to be valid when compared to the reference value. A set of recommendations and actions were agreed with the remaining participants.