Contemplated systems and methods significantly improve friction stir welding of hard metals and particularly steel and stainless steel. Among other factors, the inventors found that high transverse velocity of the tool is critical to obtain predictable and desirable weld quality, which is preferably achieved in such materials by minimizing spindle run out. Moreover, the transverse and angular velocities are preferably selected such as to achieve a temperature in the weld that is below the phase change temperature and/or the solid state transformation point of the materials.