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A tool is a tool is a tool. Isn’t it? Well, yes and no. A tool, almost any tool, can be designed in different ways to look or function differently for any reason, may it be appearance or functionally. But let’s put aesthetics aside and focus on function and ergonomics. “Function” doesn’t need to be explained, right? The tool needs to do its job properly. But what is “ergonomics”? And where does it come into play when talking about hand tools?
“Ergonomics” is a combination of two Greek words - “Ergon” meaning “work” and “Nomos” meaning “Laws”. In our day and age, when talking about “Ergonomics”, we refer to the science of designing tools, furniture and other work related products to improve efficiency while reducing discomfort and risk of injury.
What is the need for ergonomically designed products? That is a good question. The simple answer is that since tools have evolved and became more complex and job specific, the user interaction faces challenges. Over time and experience it has been found that improper hand tool selection and use may result in injuries, unequal quality of work and decreased efficiency and productivity.
How does that work and what makes a hand tool ergonomic? Ergonomically designed hand tools take into account a variety of factors, all geared to minimize muscle injuries, or more specifically injuries of the tendons, joints and nerves that typically occur over time and may affect various body parts, depending on use.
In order to avoid, or the very least minimize the risk of injury, ergonomically design hand tools are designed with consideration of weight, handle, shape and other factors carefully planned for the individual’s tool use.
A tool’s weight and its load distribution is an important factor in ergonomically designed hand tools. A tool’s weight affects the way it is being held and used. Elements to consider include how the tool is used – with one hand or two; what is the time length the tool is being held each time; precision. For tools operated with one hand, it is recommended to keep the tool’s weight under 3 pound. For a precision operation a tool should weigh under 1 pound.
The load distribution of the tool should take into account the comfort of gripping in the orientation that helps align the tool's center of gravity with the center of the gripping hand. Take, for example, drill tools. Drill tools that are front heavy require more effort to balance while in use. If the tool’s weight cannot be reduced to a recommended weight, or if the tool is poorly balanced, a tool balancer can be used.
Ergonomically design hand tools feature a power grip. This means that the operator aligns their fingers in a manner where they work in conjunction with each other to maximize the hand capacity.
The shape of the handle affects wrist and arm posture. The handle shape varies according to the task each tool has to perform. Taken into account are also the orientation and layout of the task as well as the workplace and its existing conditions. It is important to select a handle that will, with the specific said tool, will not require wrist flexion, extension or ulnar/radial deviation, in order to allow the user to maintain a neutral wrist posture.
Depending on how the force is exerted, the handle’s angle will vary. When the force is applied horizontally, a pistol grip is most suitable. When the force is exerted perpendicular to the straightened forearm and wrist, in other words when the force is applied vertically, it is best to use a straight handle. A task performed in the same plane and height as the arm and hand calls for a bent handle.
The length of a tool’s handle affects comfort of grip and the pressure being put on the palm of the hand. If the handle is too short it can cause compression in the middle of the palm. An ergonomically designed handle should extend across the width of the palm and preferably be 5.5 inches in length, with a minimum of 4 inches. Longer handles are recommended when wearing gloves.
For the optimal grip, handles should be shaped in a cylindrical or oval form. A handle’s diameter varies by use. Tool used with a power grip, like screwdrivers, should be 1.5 inches in diameter, with a minimum of 1.2 inch and a maximum of 1.8 inches in diameter. A tool being used with a pinch grip such as tweezers should be 0.4 inches with a minimum of 0.3 and a maximum of 0.5 inch. These diameter recommendations are geared to prevent slippage and reduce stress and impact on hands, fingers and wrists.
Double handle tools such as tongs and pliers used for crushing, cutting and gripping require a handle spam of 3 inches, with a minimum of 2 inches and a maximum of 4 inches. Tools with shorter or greater span reducer the user's maximum grip strength.
A good grip is an important factor when dealing with hand tools. Sufficient friction has to exist between the hand and handle for a good grip to be formed. The optimal materials hand tools should be made of are non-slip, non-conductive and compressible materials. A preferred material is textured rubber, for it promotes a good grip and reduces the force used to hold the tool on hand.
When dealing with power tools, electrical and heat insulation properties of the handles are an important factor, and plastics or compound rubbers are optional.
With so much to take into account when designing, and selecting hand tools, it can get confusing at time. But it is important keep in mind that ergonomic design is geared to helping the user perform the task in an easier and safer manner. Repetitive motion that may come with the task at hand, can lead to muscle injuries, and avoiding those is the goal, along with increasing productivity and precision.