The friction stir weldin (FSW) process is an innovative technique to join metals in the plasticity field, thus not reaching the melting temperature and consequently the liquid state as it happen in traditional welding processes. It was initially applied to aluminum alloys but now it is extended to other materials like copper, steel etc. The effect of FSW T–joints for 3 mm AA6061–T6 aluminum alloy plates on mechanical and metallurgical characterization have been investigated in this work by using the nine different tool geometries that designed according to Taguchi orthogonal array. A full process would require (81) experiments, the design of experiments is performed by L9 orthogonal array (9 experiments, 4 variables, 3 levels) that suggested by Taguchi to reduce the (81) experiments to (9) effective experiments. The results are analyzing by the (S/N) ratio and (ANOVA) techniques by using the statistical programs to compare the theoretical and experimental results. Additionally, the macro and micro observations, the (HV) readings, (X–ray radiography, visual inspection, measuring of temperature, were also been performed.