S. Kihlberg et al., DISCOMFORT FROM PNEUMATIC TOOL TORQUE REACTION - ACCEPTABILITY LIMITS, International journal of industrial ergonomics, 15(6), 1995, pp. 417-426
Pneumatic shut-off nut runners may produce large reaction forces to th
e operator's hand, especially at the end of the securing of threaded f
asteners. These reaction forces depend on the shut-off mechanism, the
joint hardness, tool torque level and to some extent the physical prop
erties of the tool. The objective of this study was to find acceptabil
ity limits for the discomfort from pneumatic tool torque reaction forc
es that could be related to technical test measures of the tools. In a
study at a truck assembly industry 38 workers participated. Reaction
forces, tool handle displacements and subjective discomfort ratings we
re measured. The tools were first tested according to ISO 6544 in the
laboratory and the tool torque impulse was calculated. Strong correlat
ions between tool handle displacements (r = 0.952), reaction forces (r
= 0.981, vertical force) and ratings were found. Acceptability limits
for ratings, tool handle displacements and reaction forces were also
determined. No subject would accept to work a whole workday at a disco
mfort level over 9 on a 20-point scale and all would work a whole work
day at a discomfort level of 2. These limits could then be correlated
to the tool torque impulse measures from the technical test, thus maki
ng it possible to predict how many of the assemblers would work within
acceptance limits.