A new control variable is introduced, that when combined with previous dependent control criteria on other variables results in a control program that can create a superior weld while minimizing wear on the FSW tool, wherein the tool repeatedly experiences the same thermal and mechanical loading within specified control windows during every repeated weld sequence because flow stresses and tool loads are driven by temperature, and dependent control loops account for differences in material and heat that is transferred at different rates in varying locations throughout a friction stir weld.