In order to assess the strength and plastic properties across different weld zones, a shear testing procedure specially conceived for sampling and testing narrow weld portions, is presented in current paper. The local constitutive behaviour of the welds is assessed from local shear stress-strain curves, plotted up to large values of plastic deformation. The shear testing tool, developed in order to enable running the shear tests in a universal tensile testing machine, is described, as well as the shear sample geometry and the procedures used for strain data acquisition via Digital Image Correlation (DIC). Results of the mechanical characterisation of the nugget of AA5083 friction stir welds, produced under different welding conditions, are used to demonstrate the quality and variety of the results obtained applying the proposed mechanical characterisation technique. © 2013 Elsevier Ltd.