Friction Stir Welding (FSW) has the advantage of generating sound welds on materials that generally present low weldability by traditional fusion welding processes, such as 2xxx and 7xxx aluminum alloys. Force measurement in FSW provides significant information about the process, the machine requirements, the effect of selected parameters, and weld soundness. In this paper, an axial force measuring device was designed, built, and tested to be used in a CNC adapted system. All tests were performed using AA 7075-T6 and a butt joint configuration. The forces obtained by the device match, in profile, key values, and trends, the ones found in literature which allows to conclude that this is a functional and sufficient device for the application.