A friction stir welding (FSW) travel axis load control method and apparatus for controlling a travel axis load applied to a FSW setup during the joining of workpieces by FSW. The method and apparatus recognize that controlling certain attributes of a friction stir welding plasticized region are key to controlling the quality of the resulting weld. This invention controls any of a number of qualities associated with the plasticized region thereby producing welds having improved mechanical and aesthetic properties, as well as extending the life of the FSW tool. The method and apparatus may control the FSW process to obtain a predetermined optimum size of a heat affected zone. The plasticized region may be monitored in a number of ways including, but not limited to, force on the tool, torque applied to the tool, workpiece temperature, plasticized region physical dimension, as well as changing surface characteristics such as color and reflectivity.