An experimental investigation of torque signature signals for self-tappingscrews

The results of an experimental study on the self-tapping screw insertion pr ocess are presented. A test rig designed and constructed for measuring the torque signature signals during screw insertions is described. Experimental results for torque signature signals during general self-tapping screw fas tenings are given graphically, confirming the five-stage variation with scr ew insertion depth predicted by an earlier theoretical study. The experimen tal data provide a basis for the further development of empirical and theor etical models of the self-tapping screw fastening process, in order to form ulate and put into practice automated monitoring and control strategies.