Industrial ERG

CHAPTER 9 HAND TOOLS

LEARNING OBJECTIVE

The students will learn about hand tool designs and be able to describe the key principles of hand tool selection and how they interact to affect performance and safety. They will also be able to inform workers of the risk factors associated with powered hand tool use and methods to control or limit exposure.

BRIEF HISTORY OF TOOL MAKING

In the centuries prior to 1800, craftsmen made their own tools. The craftsmen made these tools to fit their hands, and many tools had a specialized purpose. The journeymen would teach their apprentices how to make tools in the same manner they were taught by their masters. This tradition was millennia old. Around the year 1800, the concept of interchangeable parts was developed by Eli Whitney of the Cotton Gin fame. Before that time firearms, like everything else, were manufactured one at a time and, even if the gunsmith was following a pattern, one musket might vary enough from another so that parts were not interchangeable. In fact, if a musket became broken the owner would need to find a gunsmith to fix it, instead of just replacing the broken parts. Eli Whitney won a contract to manufacture between 10,000 and 15,000 muskets in 1798. During the course of delivering on the contract, he developed the concept of interchangeable parts, though the concept was not brought to fruition until after his death in 1825. Other manufacturers truly succeeded with the concept before Whitney (Hounshell, 1984).

Making tools and manufacturing equipment standard began with Whitney, but then in the late 1800s, Fredrick Taylor took it many steps further. Frederick Taylor was the father of the concept of Scientific Management and was one of the first management consultants. Taylor felt that control of a manufacturing process should be with management and not workers. He also sought to truly standardize most all aspects of manufacturing process. Tools, workbench sizes, and door openings were all standardized based on Taylor's principles (Hughes, 1989).

These ideas of standardization are in direct conflict with ergonomics. Of course, some of Taylor's ideas were appropriate. He was the first, as obvious as it seems now, to suggest workers use a big shovel for shoveling coke used in steel making because coke is light, and a small shovel for shoveling iron ore because it is heavy. Also, he developed the concept of tool cribs and supplying the correct tool for a job for the workers instead of them bringing tools from home. However, standardizing the tool handle length and bench heights is counter intuitive to the idea of ergonomics.

The reasonable approaches outlined in this document can be directly applied to challenges such as the following:

1.

 Deciding whether to stay with traditional tool designs or opt for new designs

2.

 Evaluating the effectiveness of different designs

3.

 Choosing a tool of the right size and shape for the task and the user.

This document also contains an easy-to-use checklist for comparing tools against several design characteristics that have been shown to reduce physical stresses on the user (NIOSH, 2004).

INTRODUCTION

Nonpowered hand tools are widely used in a variety of industries including construction, manufacturing, and agriculture. National data suggests that a large number of injuries, known as musculoskeletal disorders, are attributable to hand tool use in occupational settings, resulting in unnecessary suffering, lost workdays, and economic costs. Prevention of work-related musculoskeletal disorders is a high priority.

To the untrained eye, however, it may be difficult to evaluate tools from an ergonomic point of view. The purpose of this document is to demystify the process and help employers and workers identify nonpowered hand tools that are less likely to cause injury – those that can be used effectively with less force, less repeated movement, and less awkward positioning of the body. Presented here are the ergonomic basics of hand tool use. These principles are meant to complement the ordinary process of deciding on what tool to select by knowing how it is used and the task to which it will be applied.

Some tools are advertised as “ergonomic” or are designed with ergonomic features. A tool becomes “ergonomic” only when it fits the task you are performing, and it fits your hand without causing awkward postures, harmful contact pressures, or other safety and health risks. If you use a tool that does not fit your hand or use the tool in a way it was not intended, you might develop an injury, such as carpal tunnel syndrome, tendonitis, or muscle strain. These injuries do not happen because of a single event, such as a fall. Instead, they result from repetitive movements that are performed over time or for a long period of time, which may result in damage to muscles, tendons, nerves, ligaments, joints, cartilage, spinal discs, or blood vessels.

DEFINITIONS

Figures 9.1–9.3 show some general tool definitions.

Figure 9.1  Tool definitions (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.2  More tool definitions (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.3  Still more tool definitions (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

The cost of an injury can be high, especially if the injury prevents them from doing their job.

The best tool is one that meets the following requirements:

1.

 Fits the job one is doing

2.

 Fits the work space available

3.

 Reduces the force one need to apply

4.

 Fits their hand.

Guidelines for Selecting Hand Tools to Reduce Your Risk of Injury

A. Know the job.

B. Look at the work space.

C. Improve the work posture.

A. Select the tool.

Know the Job

Before selecting a tool, think about the job you will be doing. Tools are designed for specific purposes. Using a tool for something other than it's intended purpose often damages the tool and could cause pain, discomfort, or injury. One reduce chances of being injured when they select a tool that fits the job one will be doing.

The list of tools in each category shows a few examples of tools that are most frequently used (Figure 9.4).

Figure 9.4  Tool categories (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Next, consider whether they need the tool to provide power or precision. Then select the tool with the correct handle diameter or grip span. Figure 9.5 shows the power grip style and the appropriate tool. Figure 9.6 shows tools for precision tasks.

Figure 9.5  Power grip and oblique grip (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.6  Precision grip (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Look at the Work Space

Now look at the work space. Awkward postures may cause them to use more force. Select a tool that can be used within the space available. For example, if they work in a cramped area and high force is required, select a tool that is held with a power grip (Figure 9.7). A pinch grip will produce much less power than a power grip. Exerting force with a pinch grip means one will work harder to get the job done.

Figure 9.7  Change the tool for the task (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

If they work in a cramped space, they may not be able to use a long-handle tool. Use of a long-handle tool may cause awkward postures or harmful contact pressure on the hand as they use more force. Instead, use a tool that fits within the work space. A short-handle tool can help them reach their target directly as they keep their wrist straight (Figure 9.8).

Figure 9.8  Select the correct tool for the task (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Improve the Work Posture

Awkward postures make more demands on the body. In some cases, the placement of the work piece will affect the shoulder, elbow, wrist, hand, or back posture. Whenever possible, choose a tool that requires the least continuous force and can be used without awkward postures. The right tool will help to minimize pain and fatigue by keeping the neck, shoulders, and back relaxed and arms at sides (Figures 9.9 and 9.10).

Figure 9.9  Use the correct posture for the tool being used (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.10  Change the part location to obtain the correct posture for the tool being used (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

For example, avoid raising shoulders and elbows. Relaxed shoulders and elbows are more comfortable and will make it easier to drive downward force.

Select the Tool

Over time, exposure to awkward postures or harmful contact pressures can contribute to an injury. One can reduce the risk of injury if they select hand tools that fit the hand and the job you are doing.

Tips for Selecting Nonpowered Hand Tools

Tools used for power require high force. Tools used for precision or accuracy require low force.

1. Power grip: Select a tool that feels comfortable with a handle diameter in the range of 1.25–2 in. One can increase the diameter by adding a sleeve to the handle (Figure 9.11).

1. For double-handle tools (plier-like) used for power tasks: Select a tool with a grip span that is at least 2 in. when fully closed and no more than 3.5 in. when fully open. When continuous force is required, consider using a clamp, a grip, or locking pliers ( Figure 9.12 ).

2. For double-handle tools (plier-like) used for precision tasks: Select a tool with a grip span that is not less than 1 in. when fully closed and no more than 3 in. when fully open.

3. For double-handled pinching, gripping, or cutting tools: Select a tool with handles that are spring-loaded to return the handles to the open position.

4. Select a tool without sharp edges or finger grooves on the handle ( Figure 9.13 ).

5. Select a tool that is coated with soft material. Adding a sleeve to the tool handle pads the surface but also increases the diameter or the grip span of the handle ( Figure 9.11 ).

6. Select a tool with an angle that allows them to work with a straight wrist.

Tools with bent handles are better than those with straight handles when the force is applied horizontally (in the same direction as their straight forearm and wrist) ( Figure 9.14 ).

Tools with straight handles are better than those with bent handles when the force is applied vertically.

7. Select a tool that can be used with their dominant hand or with either hand ( Figure 9.15 ).

8. For tasks requiring high force: select a tool with a handle length longer than the widest part of the hand – usually 4–6 in. ( Figure 9.16 ).

Prevent contact pressure by making sure the end of the handle does not press on the nerves and blood vessels in the palm of the hand.

9. Select a tool that has a nonslip surface for a better grip. Adding a sleeve to the tool improves the surface texture of the handle. To prevent tool slippage within the sleeve, make sure that the sleeve fits snugly during use.

Remember: A sleeve always increases the diameter or the grip span of the handle ( Figure 9.17 ).

Figure 9.11  Tool with sleeve (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.12  Open grip tool (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.13  Tools with coated handles (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.14  Tool with bent handle (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.15  Choice of right- and left-handed tools (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.16  Handle length (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.17  Grip sleeves and proper handles (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

Figure 9.18 shows tools with spring returns for aiding in opening the tools.

Figure 9.18  Spring return tools (Combination of graphics adapted from the Washington State Department of Labor and Industries guide to selecting non-powered hand tools and original Ostrom photos and graphics)

ERGONOMIC SELECTION CRITERIA FOR POWERED HAND TOOLS

Select Tools That Can Be Used Without Bending the Wrist

Use the right tool for the job. The design of the workstation and the layout of the work piece will influence their handle choice. Work surfaces may need to be angled to match the tool, or vice versa, in order to keep the body in a neutral posture. Pistol grip tools are best for work on vertical surfaces to maintain a neutral wrist posture (Figure 9.19).

Figure 9.19  Use of pistol grip tools

Select Tools That Are as Light as Functionally Possible

Tools that weigh more than 10 lb can cause extreme forearm discomfort in a few minutes. For tools heavier than 4 lb, a second handle can help disperse the weight. Tools that are used frequently and weigh more than 1 lb should be counterbalanced.

Select the right tool for the particular job to keep the person's wrist in a neutral posture.

Consider the Design of the Handle

Choose tools with vibration-damping handles (i.e., rubber, plastic, or cork). Choose handles that are located close to or below the center of gravity of the tool. Select tools with rounded and smooth handles to aid grip and with a trigger strip instead of a trigger button.

Select Tools That Will Minimize Vibration Exposure

Vibrating tools can cause vascular spasms or a constriction of blood vessels in the fingers, which then appear white or pale (Figure 9.20). Vascular constriction may lead to numbness and swelling of hand tissue, with a loss of grip strength. Vibration-induced white finger, also known as VWF or “Reynaud's phenomenon,” and hand-arm vibration syndrome (HAVS) cause tingling, numbness, or pain that can be brought on or intensified by exposure to cold.

Figure 9.20  Vibration-induced white finger

There are preventive actions that can be taken to reduce the impact of vibration:

1.

 Reduce the number of hours or days vibrating tools are used in accordance with the American Conference of Governmental Industrial Hygiene Threshold Limit Values.

2.

 Arrange tasks to alternate use of vibrating and nonvibrating tools.

1.

 Schedule tool maintenance so tools remain sharp, lubricated, and properly tuned.

2.

 Select tools that perform satisfactorily with the least vibration. Ask tool manufacturers to furnish vibration and frequency data on their tools.

3.

 Use gloves with vibration-damping materials in the palms and fingers. Ensure workers keep warm at work, especially their hands. To be effective, gloves should fit, be full finger, and comply with ANSI S3.40-2002 or ISO 10819 standards.

4.

 Use tools with vibration-damping handles.

5.

 Keep hands warm and dry.

6.

 Avoid using tobacco or stimulant drugs that may restrict blood flow to the skin by as much as 40%.

KEY POINTS

The key points of this chapter are as follows:

There are four types of hand grips:

1.

 Power – best for heavy tasks

2.

 Pinch – best for precise tasks

3.

 Oblique

4.

 Hook

Ergonomic tools:

1.

 Fits the job one is doing

2.

 Fits the work space available

3.

 Reduces the force one needs to apply

4.

 Fits the hand

When using tools you should do the following:

1.

 Know the job.

2.

 Look at the work space.

3.

 Improve the work posture.

4.

 Select the tool.

HAND TOOL CASE STUDY

Abstract

This report documents the ergonomic assessments performed on the traditional method of splicing on 4/0 electrical cable and the Melni connector to perform a splice. A master electrician performed three (3) splices using each methodology. The tasks were recorded using digital video and still photography. The data were analyzed using two methods:

1. Observational and video analysis was used to detail the steps in the procedure and to identify the ergonomic risk factors associated with each of the two (2) sets of tasks.

2. The Rapid Upper Limb Assessment (RULA) tool was also used to perform a postural analysis of the two (2) sets of tasks (Ergonomic Concepts, n.d.).

The ergonomic risk factors associated with the traditional splice method were as follows:

· Leaning forward back postures in excess of 20° for several aspects of the task

· Twisted back postures for several aspects of the task

· Repetition associated with crimping the splice

· High forces and duration when crimping the splice

· Compression of the thigh and hands when crimping the splice.

The ergonomic risk factors associated with the Melni connector splice method were as follows:

· High hand forces and twisted wrist when inserting the wire into the Melni connector to ensure it is seated

· Awkward neck posture when inserting the wire into the Melni connector

· Awkward back posture when using the channel locks to tighten the couplers

· Awkward wrist postures when tightening the gripper/seal ring on the Melni connector.

The RULA score for the traditional splice method was seven (7), indicating a person is working in the worst posture with an immediate risk of injury from their work posture and changes should obscure immediately to prevent injury. The RULA score for the most stressful aspects of the Melni connector splice method was five (5) or less, indicating a less stressful task.

The traditional splicing method took approximately 9 min to perform, while the Melni connector method took approximately 50 s to perform. Also, the Melni connector method used fewer tools and had seven (7) fewer basic steps.

The overall conclusion is that the Melni connector splice method has significant ergonomic benefit over the traditional method of performing splices on 4/0 electrical cable. The Melni method should replace the traditional method whenever feasible.

Introduction and Background

Here is an ergonomic assessment comparison of the traditional method of performing a splice connection on 4/0 gauge aluminum cable, with using the Melni connector to perform the same sort of splice. The data collection consisted of a master electrician performing three (3) cable splices using the traditional splice method and three (3) splices using the Melni connector. The Melni connector is shown in Figure 9.21. The two tasks were observed and recorded with video and with still photographs. These tasks were performed in a laboratory setting.

Figure 9.21  Melni connector

The data were analyzed using two (2) methodologies. These were as follows:

1. Using the observations, pictures, and videos of the task to identify the steps in the procedure and to identify the ergonomic risk factors associated with each of the two (2) sets of tasks. The following are traditional ergonomic risk factors(Ergonomic Concepts, n.d.):

a. Force

b. Posture

c. Repetition

d. Duration

e. Vibration

f. Compression

2. Using the RULA evaluation tool to perform a postural analysis of the two (2) sets of tasks (McAtamney & Corlett, 1993).

This report discusses the results of the assessments, the analysis of the traditional splicing task, and the analysis of using the Melni connector to perform the splicing task.

Analysis of the Traditional Splicing Task

The equipment used for the traditional splicing task is as follows:

· Wire

· Butt splice connectors

· Crimping tool

· Utility knife or utility knife and wire stripper

· Heat shrink wrap

· Heat source (propane torch or heat gun)

· Wire cutter.

The basic steps for performing the traditional splice of 4/0 gauge wire are as follows:

1. Retrieve tools.

2. Provide access to the wire that requires splicing.

3. Adjust the crimping tool to the correct splice.

4. Cut the wire.

5. Strip the insulation back approximately 2 inches.

6. Ensure wire is clean of dirt or other contaminants.

7. Slide a shrink wrap sleeve on the wire.

8. Insert an end of the wire into the end of the butt splice connector

9. Ensure the crimping tool is adjusted correctly for the butt splice connector

10. Crimp the butt splice connector using the crimping tool.

11. Rotate the wire 90°.

12. Crimp the butt splice connector.

13. Insert the other end of the wire into the end of the butt splice connector.

14. Crimp the butt splice connector using the crimping tool.

15. Rotate the wire 90°.

16. Crimp the butt splice connector.

17. Slide the shrink wrap sleeve over the splice.

18. Use the heat source to shrink the sleeve.

19. Store tools.

The total operation of these steps took approximately 9 min to perform.

The ergonomic risk factors identified in this procedure were as follows:

· Leaning forward back postures in excess of 20° for several aspects of the task

· Twisted back postures for several aspects of the task

· Repetition associated with crimping the splice

· High forces and duration of high forces when crimping the splice

· Compression of the thigh and hands when crimping the splice.

In reality, these tasks were being performed in an ideal environment to include being indoors, good lighting, and ambient temperatures in the range of 70–75 °F. In addition, the splices were performed on a table. When performed in the field, the task could be even more stressful. For instance, if the tasks were performed in a ditch or on overhead wires the postures and forces would vary greatly.

The steps of the process with ergonomic risk factors were 9, 10, 12, 13, 14, and 16. The crimping steps (10, 12, 14, and 16) appeared to be the most stressful and are discussed next.

Figure 9.22 shows a photo at the start of the crimping step. The master electrician is in an awkward posture. His torso is leaning forward, one handle of the tool is compressing his thigh, his upper arm approaching shoulder height, and he is putting a great amount of force on the handles. He must attain this posture four (4) times each time he splices one (1) 4/0 cable. So, it is performed four (4) times in a 9-min sequence of steps. Each crimping step took approximately 9 s to perform.

Figure 9.22  Start of crimping step

At the midpoint of the crimping step, as shown in Figure 9.23, the master electrician is in a very awkward posture. His back is bent forward and twisted, his neck is twisted, and he is continuing to apply a great amount of force using his body weight and his hands. His left upper arm is above shoulder height and abducted (away from the body), and the handle of the tool is in a position where it could slip.

Figure 9.23  Midpoint crimping step

Figure 9.24 shows the end point of the crimping step. As the figure shows, the master electrician is in a very awkward posture with his back leaning forward almost the end of a supportable range and twisted, his neck is in a twisted posture; handle of the tool is still unsupported and could slip, and he is still exerting a great amount of force.

Figure 9.24  End point of crimping step

The RULA analysis was peroformed on three of the most stressful postures associated with this task. Figure 9.22 shows the start of the crimping task. A RULA analysis was performed on this posture. The completed RULA form is shown in Figure 9.25. The RULA score developed from this analysis was seven (7). A seven (7) represents the worst postural score under the RULA technique, indicating a change needs to be made to the task. This step is performed four (4) times for each splice. So, this action is performed four (4) times in the 9-min task, allowing very little time for muscle recovery.

Figure 9.25  Example of a completed RULA form for crimping

Figure 9.23 shows the midpoint in the crimping task. The completed RULA form is shown in Figure 9.26. The RULA score developed from this analysis was seven (7). A seven (7) again represents the worst postural score under the RULA technique, indicating a change needs to be made to the task. This step is also performed four (4) times for each splice. So, this action is performed four (4) times in the 9-min task.

Figure 9.26  Another completed RULA form example

Figure 9.24 shows the final phase of the crimping step and Figure 9.27 shows the RULA analysis. This part of the crimping task also scored a RULA score of seven (7).

Figure 9.27  Completed RULA analysis form

As stated above, a RULA score of seven (7) is the worst postural score possible using this methodology. This score indicates that the task should be modified immediately to avoid injury.

Analysis of Using the Melni Connector to Perform a Splice

The equipment used for the Melni connector splicing task is as follows:

· Wire

· Melni connector

· Two (2) pairs of channel lock pliers.

The basic steps for performing the splicing task with the Melni connector for 4/0 wire are as follows:

1. Retrieving tools

2. Providing access to the wire that requires splicing

3. Cutting the wire

4. Stripping the insulation back approximately 2 in.

1. Ensuring the wire is clean of dirt or other contaminants

2. Inserting an end of the wire into the end of the Melni connector

3. Hand tightening the gripper/seal ring on the Melni connector

4. Inserting the other end of the wire into the end of the Melni connector

5. Hand tightening the gripper/seal ring on the Melni connector

6. Twisting the couplers on one end of the Melni connectors with the channel lock pliers

7. Ensuring the coupler on the other side of the connector is tight

8. Storing tools.

The procedure for using the Melni connector has seven (7) fewer basic steps, and the steps have many fewer ergonomic risk factors. This process took approximately 50 s to perform, meaning duration is not a factor as it is with the traditional method. From observing the task and analyzing the videos, the steps with ergonomic risk factors were steps 6–10. The ergonomic risk factors for the steps were as follows:

· High hand forces and twisted wrist when inserting the wire into the Melni connector to ensure it is seated (steps 6 and 8)

· Awkward neck posture when inserting the wire into the Melni connector (steps 6 and 8)

· Awkward back posture when using the channel locks to tighten the couplers (step 10)

· Awkward wrist postures when tighten the gripper/seal ring on the Melni connector (step 9).

As with the traditional method, the postural issues will also depend on the environment where the splice is being performed. The conditions of this test were considered ideal.

Figure 9.28  shows the most stressful step using the Melni connector. This figure shows that the master electrician is slightly bent forward, and he is using force to push the wire into the Melni connector.

Figure 9.28  Inserting wire into Melni connector

Figure 9.29  shows the posture when using the channel locks to tighten the Melni connector couplings.  Figure 9.30  shows the posture when the master electrician tightens the gripper/seal ring on the Melni connector.

Figure 9.29  Tightening coupler step for Melni connector

Figure 9.30  Tightening gripper/seal ring step for Melni connector

The resulting RULA scores were 5, 4, and 4, respectively, indicating that the stress should be further investigated and changed at some point in time but is not considered imminent as with the traditional method.

Figure 9.31  shows the RULA analysis for wire insertion step.

Figure 9.31  RULA analysis for wire insertion step

Key Points

The results from the analysis showed the following points:

· There were seven (7) fewer steps associated with the Melni connector for performing a splice of 4/0 cable.

· The time to perform the splicing task was approximately 8 min less for the Melni connector compared with the traditional splicing method.

· The ergonomic hazards associated with using the Melni connector were fewer in number and, according to the RULA analyses, less stressful. The RULA scores for the three (3) parts of the crimping steps for the traditional splicing method all were seven (7), whereas the highest RULA score for any of the steps associated with the Melni connector was five (5).

· The risk of the crimping tool slipping while performing the crimping steps for a traditional splice appears to be great and could lead to an acute injury.

· The only tools required to perform the Melni connector splice are two (2) channel locks.

The overall conclusion is that the use of the Melni connector provides great ergonomic benefit over the traditional method of splicing 4/0 cable and takes considerably less time to perform. It is recommended that this method be used whenever possible and electricians should be trained on the ergonomic risk factors associated with this tasks as well as stretching techniques to reduce fatigue.

REVIEW QUESTIONS

1. What is the best grip for tasks requiring high forces?

2. What is the best grip for precision tasks?

3. Are low-power tools the answer to ergonomic issues?

REFERENCES

1. Ergonomic Concepts. (n.d.). Retrieved 2015, from Ergoweb:  http://ergoweb.com/knowledge/ergonomics-101/concepts/ .

2. Hounshell, D. A. (1984). From the American System to Mass Production. Baltimore: Johns Hopkins University.

3. Hughes, T. P. (1989). American Genesis: A Century of Invention and Technological Enthusiasm. Penguin.

4. McAtamney, L., & Corlett, E. N. (1993). RULA: A Survey Method for the Investigation of Work-Related Upper Limb Disorders. Applied Ergonomics, 24(2), 91–99.

5. NIOSH. (2004). A Guide to Selecting Non-Powered Hand Tools. NIOSH, p. 164.