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We use hand tools on a daily basis at home and
at work, whether for hanging a picture, opening
a bag of milk or performing tasks at work. Prolonged
use of "non-optimal" hand tools can often
be linked to Repetitive Strain Injuries (RSIs).
The following are reasons hand tools can lead to
RSIs or discomfort:
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Result in repetitive or static
hand work |
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Require awkward postures |
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Have sharp edges |
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Are heavy & unsuspended
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Exert force to the hand |
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Vibrate |
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Have a poor handle design |
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Are improper tool for the task |
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| Hand tools should fit the characteristics
of the user and be suitable for the task.
The handle of the tool should fit the dimension
of the hand and optimize the users own strength
and motion capabilities. As working populationâs
range in size, so must the tools being used.
The following criteria should be evaluated
before selecting a tool for a job: |
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Tool dimensions: size, weight
& shape |
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Posture required for use |
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Tool handle design |
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Vibration, exhaust emissions
and/or torque reaction forces |
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Worker characteristics |
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| As the handle of a tool is the interface between
the tool and the user, the design of the handle
can contribute significantly to the effectiveness
of the tool. The grip of a tool will often dictate
its use. For instance, smaller tools with a precision
grip are often used in fine manipulation tasks.
Tools that allow for a power grip are better to
exert force. Thus, the relationship between handle
size and hand size is important. If the handle is
too long for the hand, increased force will be placed
on the wrist joint. If the handle is too small,
pressure points can occur in the muscle tissues
of the hand and fingers.
When evaluating a hand tool, it is important
to assess if the tool is promoting awkward postures
of the hand, arm and back. The wrist should be
kept straight to avoid overexertion of tissues,
tendons, nerves and blood vessels. A tool causing
awkward postures may be deficient in the grip,
size or may be an improper choice for the task.
It is always best when selecting a tool that
the user be considered first and foremost. Approximately
92% of the population is right handed, however
that does not mean that the remaining 8% of the
population should be ignored. Hand tools should
be selected so that they can be used with the
right or left hand and accommodate the size and
shape of the hand. |
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| The following are several general
design rules for hand tools: |
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Push or pull in the direction
of the forearm, keeping the wrist straight |
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Provide good coupling between
hand and handle by shape and friction |
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Avoid pressure and pinch points
in the handle |
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Use rounded and padded surfaces |
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Avoid tools that transmit vibration
to the hand |
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Do not operate tools frequently and forcefully
by the hand |
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| (Kroemer et al., 2001)
With increases in workload and repetitive work
it is essential that we use the proper tools.
For a free Ergonomic Tool Evaluation Audit
contact ERGO Inc.
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