HBM’s RY61M strain gage hole-drilling rosette is used to determine residual stresses in components. The strain gages determine the deformation, or relaxation strain, around a drill hole while the hole is being inscribed. The unit’s structure increases the accuracy of residual stress measurement by using six measuring grids instead of the typical three. The grids are arranged around the drill hole, with each of the opposite SG pairs interconnected so that their signals are averaged. The measurement error resulting from drill-hole eccentricity is reduced by a factor of five.