Study of torque, axial tension and bending moment during the screw tightening (1st report) - Relation between torque on fitted portion of threads andaxial tension

This paper deals with the relation between the tightening torque on the scr ew threads and axial tension in the elastic-region tightening. The torque o n the fitted portion of threads and clamping force of the screw sizes M12x1 .5-M20x2.5 are measured by the tightening tests using a new designed device . The experimental results indicate that these measurement values are relat ed to each other through the general equation that expresses the relation b etween the torque on the fitted portion of the threads and axial tension in the screw threads. It is concluded that the validity of the general equati on is confirmed experimentally. However, the general equation is not applic able when a bending moment acts on the bolt at the time of tightening.