4 Factors in Ergonomic Hand Tool Design

Each year, workers in the US injured by “repetitive use of tools” miss an average of 6.7 days of work (Bureau of Labor Statistics, 2010). Since OSHA holds each employer “responsible for the safe condition of tools and equipment used by employees, including tools and equipment which may be furnished by employees” (2010), workers and their employers have a vested interest in hand tool safety. As designers and manufacturers of hand tools, we can capitalize on this ever-present concern by developing more ergonomic tools.

So, what makes a hand tool ergonomic? The Canadian Center for Occupational Health and Safety (CCOHS) denotes four major concerns in ergonomic hand tool design.

1. Weight

To be considered ergonomic a hand tool should be light weight and easy-to-use. Ideally:

• Workers should be able to operate a tool with one hand.
• The weight of the tool should not exceed 2.2 kg.
• The center of gravity should be aligned with the center of the gripping hand.

(CCOHS, 2005)

2. Power

Power tools reduce the amount of effort put forth and, therefore, may reduce strain on and risk of injury to the user. However, power tools are not always suitable replacements for hand tools. Power tools are typically heavier and more bulky than hand tools; this added weight can be an additional source of stress/strain.

3. Handles

The one aspect of tool design with the most ergonomic considerations is handle design.

• Handle Shape

As a rule of thumb, a good handle shape design should “bend the tool, not the wrist.” (CCOHS, 2005) The best handle designs eliminate unnecessary wrist rotation.

• Diameter

In general, handles should be cylindrical or oval in cross section, with a diameter of between 30 mm and 45 mm (CCOHS, 2005).

• Length

The CCOHS recommends that tool handles be longer than 100mm; a handle that is too short can cause unnecessary compression in the middle of the palm (2005).

• Separation between Handles

Tools with two handles, like pliers or tongs, should have handle spacing between 50 mm and 65 mm apart to prevent carpal tunnel syndrome (CCOHS, 2005).

• Power Tool Triggers

Tools should be designed to prevent “trigger finger” or “trigger thumb”. Ideally, they should require two or three fingers for operation, rather than one. 50mm is the recommended minimum length for a trigger (CCOHS, 2005).

• Materials and Textures of Handles

Handles should be designed of material that allows the user to get a good grip. In addition, edges should be rounded out to prevent cuts. The CCOHS recommends plastic, rubber, and other soft, non-slip materials for handles (2005).

4. Vibration

The best way to minimize vibration in power tools is to design the tool using materials, like rubber, that help deaden vibrations (CCOH 2005).

Designing hand tools for the future means designing for the job and user. Simple ergonomic innovations like product material, sizing, and intuitive design can be the difference between a good hand tool and one that you can’t keep on the shelves.

Works Cited

Agrability Project. (2003). What to Look for When Selecting or Modifying Hand Tools to Provide a Better Fit with the User. http://www.ergo-eg.com/uploads/books/selecting%20or%20modifying%20hand%20tools.pdf

Bureau of Labor Statistics, United States. (2010). Survey of Occupational Injuries and Illnesses in cooperation with participating State agencies. http://www.bls.gov/iif/oshwc/osh/case/ostb2516.txt

California Department of Industrial Relations and the National Institute for Occupational Safety and Health. (2004). Easy Ergonomics: A Guide to Selecting Non-Powered Hand Tools. http://www.humanics-es.com/ErgonomicHandTools.pdf

Canadian Centre for Occupational Health and Safety. (2010). Tool Design. Retrieved from http://www.ccohs.ca/oshanswers/ergonomics/handtools/tooldesign.html

Occupational Safety & Health Administration (OSHA). Regulations: Hand and Portable Power Tools and Other Hand-held Equipment. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9849

Hedge, Alan. Cornell University. (August 2010). Hand Tool Design. Retrieved from http://ergo.human.cornell.edu/studentdownloads/DEA3250pdfs/Hand%20Tools.pdf

Miller, Stephani. (2002) Power Tools Go Ergonomic. Remodeling Magazine, November. http://www.remodeling.hw.net/tools-and-equipment/power-tools-go-ergonomic.aspx

Schwartz, Bill. (1994). Proper Ergonomics Integral to the Design of Power Tools. Construction Dimensions, December. http://www.awci.org/cd/pdfs/9412_a.pdf