Ergonomics - Atlas Copco

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Handle size
Since a tool handle usually houses a
number of functions, such as an air inlet, a
trigger and reverse control, a noise muffler
and an outlet valve, handle design must
always be a compromise.
For instance, if the designer wishes to
reduce the circumference of the handle, the
volume of the noise muffler must also be re-
duced, with increased noise levels as a result.
The length of the handle
As mentioned earlier, the fingers and center
of the palm are sensitive to high pressure.
Therefore the handle should be sufficiently
large to distribute the forces in play over the
palm and across the fingers.
Studies of the breadth of male and female
hands indicate that the palmar force-bearing
area should be at least 90 mm long to ensure
that palmar forces are primarily supported by
the muscles on each side of the palm. A gen-
eral recommendation for the handle length
of tools where appreciable forces are to be
applied is about 100 to 130 mm.
When high accessibility is important,
the lower end of the size range may be pre-
ferred. If a tool is specifically intended for
female operators, a shorter handle length
may be selected. The optimal handle length
for female operators is about 90 to 110 mm
and no shorter than 80 mm. When tools
are used with gloves, an additional 10 mm
should be added.
Handle diameter
Handle diameter is the main factor influ-
encing the operator’s capacity to generate
force. When grasping a large tool handle,
the force applied from the fingertips can be
two or three times greater than the force
applied from the inner part of the fingers.
On the other hand, if an object is too small,
the fingers cannot effectively apply force to
it, partly because the finger flexor muscles
are foreshortened and lose their contractile
capability to produce tension. For circular
handles the following dimensions are recom-
mended:
l Power grips: recommended diameter of
38 mm for men and 34 mm for women;
acceptable range from 30 to 45 mm;
l Precision operations: recommended
diameter of 12 mm; acceptable range
from 8 to 16 mm.
Straight screwdrivers may be given a coni-
cal form. The operator can select different
positions on the handle and in that way
change the diameter depending on the type
of work to be performed. An end stop is a