A hand tool has an elongated shank with a handle at one end and a bit holder at the other end, the bit holder including a cylindrical body having a distal end surface and an axis, the body having an axial bore formed in the end surface of non-circular transverse cross section and terminating at an inner end surface. The energy storage is arranged directly within the hermetically tight housing without having a separate housing. Reducts are calculated from a subset of the best-performing columns of the partitioned and labeled training set data. The diffusing protrusions are hemispherical or sub-hemispherical, and a diameter of each diffusing protrusion is in the range from 10 \u03bcm\u02dc50 \u03bcm.