In this research, both neutron and synchrotron X-ray diffraction techniques have been used to investigate variations in measured d spacing in two reference samples. The reference stress-free samples, a set of cubes and a comb sample, were produced using electrodischarge machining (EDM) to obtain a macro-strain-relieved condition. It is shown that there is a variation in microstructure across the parent metal, heat-affected zone (HAZ) and weld metal. A study of the issues in using the cubes and comb sample to provide reference do values for the measurement of residual stress in welding is presented. (c) 2006 Elsevier B.V. All rights reserved.