A portable boring machine includes: a transmission unit comprising a first electric motor having an axis of rotation (B) and a distribution block of the motion imparted by said electric motor to a tools shaft supporting means for boring and welding and having an axis of rotation (C); a centralized unit comprising a supporting shaft for advancement of said tools shaft formed by a hollow cylindrical tube internally comprising an externally threaded screw tube, and a second centralized electric motor adapted to manage said advancement; means for coupling and decoupling said transmission unit from said centralized unit. The portable boring machine further comprises an advancement system of said screw tube configured for converting the rotary motion imparted by said electric motor in straight linear motion of said screw tube along said axis (C).