Abstract. This report describes the results obtained from a supplementary comparison on the thermal expansion coefficient of gauge blocks in 2004–2006. The comparison was carried out by members in DG8 of CCL. The four gauge blocks, which were three ceramics blocks and one steel block, were calibrated by seven organizations in turn. Most reported results corresponded with each other within their expanded uncertainties (k = 2). However, some results for the steel gauge block had a systematic deviation from the key reference value. It was considered that the source of the deviation was mainly caused by the capability of the temperature determination of the gauge block.

Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the APMP, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).