Ergonomics - Atlas Copco

Shock reaction
A shock reaction in a tool is an external
load placed on the operator for an ex-
tremely short period of time. Tools gen-
erating this type of load during use are
typically angle nutrunners and screw-
drivers. Drills can also generate a shock
at the moment when the bit penetrates
the workpiece. The unprepared operator
can lose his grip on the tool, his fingers
may be crushed, or he may receive a
blow from the tool.
What is a shock?
A shock and its reaction happen during a
short period of time. Events happening during
less than 300 ms can be defined as shocks.
During this short period an operator is unable
to influence the course of events. A tightening
cycle lasting longer than 300 ms also subjects
the operator to a shock reaction, but that load
should be handled according to the methods
Rapid motions of the hand-arm system
are perceived as shocks.
outlined in the section on external loads.
The hand-arm system can be considered
as a passive mass spring system – in par-
ticular a mass. The shorter the shock, the
smaller the reaction or response in the
machine and hand-arm system. If the dura-
tion of the shock is gradually increased, the
reaction will also increase. Depending on
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