A field investigation of manual forces associated with trigger and push to start electric screwdrivers

Abstract

This study investigated manual forces associated with trigger start (TS) and push to start (PTS) activation in-line electric screwdriver designs. The vertically directed axial screwdriver force transmitted with the driver to the fastener and the grip/finger forces on the driver handle were measured from 13 employees in an electronics assembly manufacturing facility. The PTS driver was associated with significantly (p <.01) higher axial force than the TS driver at two of the four workstations, where the difference was as high as a 184% increase (36.5 vs. 103.8 N). Total finger force on the screwdriver handle was also higher for the PTS screwdriver (p <.01). The PTS screwdriver may reduce instances of fastener head damage ("cam out") by requiring a minimum level of axial force to ensure better contact between the screwdriver bit and the fastener. However, this appears to come at the expense of greater manual forces exerted by the operator.