PNEUMATIC TOOL TORQUE REACTIONS - REACTION FORCES, TOOL HANDLE DISPLACEMENTS AND DISCOMFORT RATINGS DURING WORK WITH SHUTOFF NUTRUNNERS

Reaction forces, hand-arm displacement and subjective ratings were stu died during securing of threaded fasteners with nine right-angle nutru nners. The nutrunners had three different preset spindle torques and t hree different shut-off mechanisms. The tools were tested according to the international ISO method and with a method proposed by the author s in a previous study. Twelve mate subjects participated in the study. A force platform measured the reaction forces between the subjects an d the floor. Motions of the hand-arm system and shoulder were measured with an optoelectronic measuring system and a goniometer. Strong corr elations between motions/ground reaction forces and ratings were found . The ratings were also strongly correlated with the tool torque impul se, calculated according to ISO 6544, as well as with the time for whi ch the torque exceeded 75% of the preset spindle torque multiplied by the preset spindle torque to produce a 'time-torque value'. The strong est correlation, though, was found with the time-torque value, but the difference was not large enough to propose a change of the ISO standa rd.