Table of Contents

Expand all Collapse all

Easy Ergonomics: A Guide to Selecting Non-Powered Hand Tools

The information on this page is drawn from material produced by the NIOSH/CDC/Cal OSHA. The original pdf is available at the bottom of the page. 6/1/09

Background

Non-powered 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 for both the National Institute for Occupational Safety and Health (NIOSH) and the California Occupational Safety and Health Administration (Cal/OSHA). Both agencies recognize the importance of design and selection of hand tools in strategies to reduce injuries of this type.

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 non-powered 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.

The reasonable and common-sense approaches outlined in this document can be directly applied to challenges like these:

deciding whether to stay with traditional tool designs or opt for new designs
evaluating the effectiveness of different designs
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. We hope this checklist and the accompanying background material will be of practical use to all who wish to select tools that get the job done more safely, comfortably, and productively.

Definitions

Awkward Postures

Postures that strain the neck, shoulders, elbows, wrists, hands, or back. Bending, stooping, twisting, and reaching, are examples of awkward postures.

Power Grip

The hand grip that provides maximum hand power for high force tasks. All the fingers wrap around the handle.

Contact Pressure

Pressure from a hard surface, point, or edge on any part of the body.

Pinch Grip

The hand grip that provides control for precision and accuracy. The tool is gripped between the thumb and the fingertips.

Single-Handle Tools

Tube-like tools measured by handle length and diameter.

Double-Handle Tools

Plier-like tools measured by handle length and grip span.

Grip Span

The distance between the thumb and fingers when the tool jaws are open or closed.

The Best Tool

Fits the job you are doing
Fits the work space available
Reduces the force you need to apply
Fits your hand
Can be used in a comfortable work position

Signs of a problem with your tool use

Tingling
Swelling in the joints
Decreased ability to move
Decreased grip strength
Pain from movement, pressure, or exposure to cold or vibration
Continual muscle fatigue
Sore muscles
Numbness
Change in the skin color of your hands or fingertips

These symptoms may not appear immediately because they develop over weeks, months, or years. By then, the damage may be serious. Take action before you notice any symptoms.

Know Your Job

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

Cutting, pinching, gripping tools

Pliers
Snips
Cutters

Striking tools

Hammers

Driving tools

Screwdrivers
Hand wrenches
Nut drivers
T-handle wrenches

Struck or hammered tools

Punches
Chisels
Nail sets

Next, consider whether you need the tool to provide power or precision. Then select the tool with the correct handle diameter or grip span.

Power tasks

Single-Handle Tools

HANDLE DIAMETER for power tasks is 1 1/4 inches to 2 inches

Double-Handle Tools

OPEN GRIP SPAN for power tasks is not more than 3 1/2 inches
CLOSED GRIP SPAN for power tasks is not less than 2 inches

Precision Tasks

Single-Handle Tools

HANDLE DIAMETER for precision tasks is 1/4 inch to 1/2 inch

Double-Handle Tools

OPEN GRIP SPAN for precision tasks is not more than 3 inches
CLOSED GRIP SPAN for precision tasks is not less than 1 inch

Look at Your Work Space

Now look at your work space. Awkward postures may cause you to use more force. 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 much less power than a power grip. Exerting force with a pinch grip means you will work harder to get the job done.

If you work in a cramped space, you 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 your hand as you use more force. Instead, use a tool that fits within the work space. A short-handle tool can help you reach your target directly as you keep your wrist straight.

Improve your work posture

Awkward postures make more demands on your body. In some cases, the placement of the work piece will affect your 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 you to minimize pain and fatigue by keeping your neck, shoulders, and back relaxed and your arms at your sides.

For example, avoid raising your 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. You can reduce your risk of injury if you select hand tools that fit your hand and the job you are doing.

Tips for Selecting Hand Tools

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

For single-handle tools used for power tasks: Select a tool that feels comfortable with a handle diameter in the range of 1 1/4 inches to 2 inches. You can increase the diameter by adding a sleeve to the handle
For single-handle tools used for precision tasks: Select a tool with a handle diameter of 1/4 inch to 1/2 inch.
For double-handle tools (plier-like) used for power tasks: Select a tool with a grip span that is at least 2 inches when fully closed and no more than 3 1/2 inches when fully open. When continuous force is required, consider using a clamp, a grip, or locking pliers.
For double-handle tools (plier-like) used for precision tasks: Select a tool with a grip span that is not less than 1 inch when fully closed and no more than 3 inches when fully open.
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.
Select a tool without sharp edges or finger grooves on the handle.
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 (see 1, 2, 3, or 4 above).
Select a tool with an angle that allows you 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 your straight forearm and wrist).

Tools with straight handles are better than those with bent handles when the force is applied vertically.
Select a tool that can be used with your dominant hand or with either hand.
For tasks requiring high force: Select a tool with a handle length longer than the widest part of your hand - usually 4 inches to 6 inches. Prevent contact pressure by making sure the end of the handle does not press on the nerves and blood vessels in the palm of your hand. If the handle is too short, the end will press against the palm of your hand and may cause an injury.
Select a tool that has a non-slip 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 (see 1, 2, 3, or 4 above).