Ergonomics - Atlas Copco

integrated over an eight-hour working day
must not be confused with the emission val-
ue 2.5 m/s 2 , above which the manufacturer
must declare the vibration emission value.
For more information, please refer to the
Atlas Copco Pocket Guide Vibration exposure
assessment for industrial power tools.
Vibration control
Power tool design involves a large number
of parameters. The solution chosen reflects
the designer’s view of an optimal compro-
mise on all parameters. One of these param-
eters is vibration.
The appearance of oscillating forces
These forces can arise in the tool itself,
from the inserted tool or from the process in
which the tool is used. A typical example of
a power tool with built-in oscillating forces
is a percussive tool where a piston is moved
backwards and forwards in a cylinder. The
motion is caused by compressed air acting on
the front or back end of the piston, and at the
same time acting with a reaction force on the
machine housing. This oscillating force on
the housing produces a vibration.
Other examples are internal unbalanced
rotating parts. Vibrations can arise from
shocks due to badly designed gears or from
badly designed counter-weights in oscillating
sanders. When designing power tools, oscil-
lating forces in the design concept must be
avoided or offset.
Such forces need not be of high magni-
tude – a force of just a few Newtons can be
large enough to initiate an unacceptable vi-
bration in a machine housing and its handle.
Grinding wheel imbalance is one of
the main sources of vibration.
Vibration can also be caused by imbalance
of the inserted tool. For example, vibra-
tions in hand-held grinding machines arise
mainly from the imbalance of the grinding
wheel. This imbalance depends on the qual-
ity of the wheel and its precise fit on the tool
spindle. Since the tolerances of the center
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