An object is to improve accuracy of tightening torque and to shorten time necessary for fastening a screw in an impact type screw fastening device that uses an electric motor as a rotation driving source. A control method for the impact type screw fastening device that uses an electric motor as a rotation...http://www.google.com/patents/US20090014192?utm_source=gb-gplus-sharePatent US20090014192 - Control method and control unit for impact type screw fastening device
