FIELD: threaded joint tightening tools. SUBSTANCE: power nut-driver is provided with a cluster gear that is engageable on one side with an electromagnetic clutch, and on the other side - with a spindle, thrust bearing and piezoelectric transducer located inside the key button; the spindle is made hollow. The piezoelectric transducer through the spindle is connected to a transceiver, using a pulse generator and amplifier, and connected to the time interval beginning and end units, data conversion unit, and data register of the automatic tightening torque control system. EFFECT: enhanced precision and quality of threaded joint tightening by enhancing the stability of tightening torque control in the process of assembly of threaded joint with employment of an ultrasonic system. 3 dwg
