Selecting the Right Tool For the Job, Part 2
How Tools Interact in the Environment

As discussed in last month's Ergo Tip of the Month, there are many challenges in selecting the right tool for the job. Minimizing risk factors is the key principle to sound ergonomic practices. Before you select a tool, also think about the environment in which the job will be completed.

Tools in their Environment

Prior to selecting a tool for the job, you need to survey your work environment. An undesirable working area can result in awkward postures which in turn cause you to use more force than is needed. Select a tool that can be used within the space available. For example, if you work in a cramped area and high force is required, select a tool that is held with a power grip. A pinch grip will produce less power and you will work harder to get the job done.

Posture

When selecting a tool, you want to keep the posture of the worker as close to neutral as possible and avoid awkward postures (such as reaching overhead, bending forward, twisting, etc.). The strain on the body increases as the worker's posture moves away from neutral. This strain is a combination of the weight in the hands and how far away it is held. The following are some examples of how tool selection can affect posture:

Static Loading

The risk associated with holding a sustained posture, also known as ‘static loading’, increases as the posture is held for longer periods of time. Statically loaded muscles are more vulnerable to fatigue and subsequent injury than muscles which are performing dynamic work involving movement.

Torque

When using power tools it is recommended to use balancers wherever possible to offset the weight of the tool. Unbalanced tools add realized weight to the operator’s upper extremity and cause unnecessary physical stress on the wrist, elbow and shoulder joints.

Joint tightening/fastening is dependent on the operator’s capacity to react against torque. In response to torque reaction, substantial grip forces are exerted by the operator to stabilize the wrist, limit tool rotation, and prevent tool slippage.

Recommended Ergonomic Guidelines for Power tool usage are:

• A reaction device is recommended for the following:

  • In-line tools with a torque higher than 3.2 Nm.

  • Pistol grip tools with a torque higher than 7 Nm for air/clutch and higher than 9 Nm for DC.

  • Right angle tools with torque higher than 55 Nm.

• Two hands are required during the securing cycle of a right angle tool in order to assist with torque reaction.

• All air tools should be clutch versus air stall. While battery tools are DC electric, those using clutches for shut off MUST follow air tool torque limits listed above.

Vibration

Avoid tools that subject you to high levels of vibration. The most widely studied and most common type of vibration exposure is Hand-Arm Vibration (HAV). Workers may be exposed to HAV when operating hand-held power tools or when holding materials being worked by machines. Exposure may result in a range of health effects collectively known as Hand-Arm Vibration Syndrome or HAVS. The most well known health effect is vibration white finger, but other effects include damage to sensory nerves, muscles and joints in the hands and arms.

When selecting a power tool:

• Avoid long term exposure to vibration

• Avoid tools with long extensions

• Avoid tools that do not meet ISO standards for Hand-Arm vibration

• Select a manual tool (when applicable) over a vibrating tool

Tools are designed for specific purposes; using a tool inappropriately can result in pain, discomfort, or injury. By considering the right tool for the job and the job environment you will be taking a significant step forward in reducing the risk of injury.

References

"Easy Ergonomics:  A Guide to Selecting Non-Powered Hand Tools"  California Department of Industrial Relations.

http://www.dir.ca.gov/dosh/dosh_publications/handtools.html.  (April 8, 2010)

Avoiding Injury While Using Tools Part III: Guide to proper tool use and planning the project

http://www.working-well.org/articles/pdf/ToolUse.pdf

"Tool Design."  Canadian Centre for Occupational Health and Safety. 

http://www.ccohs.ca/oshanswers/ergonomics/handtools/tooldesign.html.  (April 8, 2010).

http://en.wikipedia.org/wiki/Hand-arm_vibration_syndrome

Sandalwood is an engineering and ergonomics consulting firm. Sandalwood designs and executes strategic programs for manufacturers which reduce their work-related risks to quality, productivity and employee health. By providing knowledge, research, technology and resources, Sandalwood supports its clients from the executive level to the factory floor. The Ergo Tip of the Month is offered to our customers and friends for the benefit of the Ergonomics community and is to be used entirely at the discretion of the recipient. To request information on our services, click here.