Hand Tool Selection and Design for Usability, Safety, and Health

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Hand Tool Selection and Design for Usability,
Safety, and Health

• Robert Stuthridge B.Sc., M.Sc.
• Ergonomist
• National AgrAbility Project
• Purdue University
• West Lafayette, IN

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Agenda

• Ergonomic risks from using hand tools
• Design features of hand tools affecting risk
• Trial and error vs. formal evaluation of tools
• Poll What factors influence your hand tool
  choices?
• Ergonomic checklist evaluation of hand tools
• Practical evaluation of commonly used hand tools
  using the ergo checklist
• Findings
• Feedback and questions

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Ergonomic Risks from Hand Tools

• 1982-1986 433,000 emergency room visits due to
  injuries caused by hand tools
• 12 of all ER visits (Dababneh et al, 2004)
• 9 of all occupational injuries due to hand tools
  (Aghazadeh and Mital, 1987)
• Mainly extremities affected.
• Most injuries from non-powered tools, especially
  knives, shovels, axes.
• Vibrating hand tools (esp. saws) HAVS. Excessive
  grip force increases risk of cumulative trauma
  disorders such as carpal tunnel syndrome due to
• involuntary tonic reflex of muscles at certain
  frequencies increases musculoskeletal loading
  by up to 100 compared with non-vibrating tool

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Risks for Hand Tool Use in Agriculture

• Non-powered hand tool injury rates highest in
  Agriculture
• Powered hand tool injury rates second highest in
  Agriculture
• Construction
• Agriculture
• Manufacturing
• Mining

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Hand Tools Defined

• Hand tools are
• Portable
• Manipulable
• Supported completely or partially by the hands.
• Tool is applied to the raw material rather than
  vice versa (so the hand tool is usually the part
  that is moving).

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Design features affecting risk

• Handle design grip/slip
• Handle design smooth/sharp edges
• Handle design insulated or not (electrical,
  cold)
• Handle design grip length
• One-handle tools - cross sectional size of handle
  
• One-handle tools - cross sectional shape of
  handle
• Two-handle tools grip span dimension
• Angle of handle wrist angle
• Weight of tool
• Handedness of tool either hand
• Handedness of tool suitability for dominant
  hand
• Tool design allows use of two hands
• Color (visibility) of tool and its accessories in
  work environment

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Trial and error vs. formal evaluation of tools

• Tools are expensive to buy.
• Poor ergo design increases risk thinking about
  design is too late once injury has occurred.
• Design hazards are not often evident using
  common sense (or poorly designed tools would
  not be bought and used).
• Some risk evaluation may be applied in retail
  stores, but what about buying/specifying via mail
  order and the internet?
• Formal risk evaluation skills help when
  specifying tools for other users.

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Ergonomic checklist evaluation of hand tools
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Practical evaluation of commonly used hand tools
using the ergo checklist

• Eight types of tools - Eighteen tools in all
• Snips (2)
• Pliers (2)
• Utility knife (2)
• Axe (2)
• Hacksaw (2)
• Screwdriver (3)
• Caulking gun (2)
• Hammer (3)

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Practical evaluation using checklist

• Nine groups, 1-9
• Each group evaluates two different tools labeled
  AB, CD, EFQR etc., for five minutes per tool.
  Group 1AB, Group 2CD,,Group 9QR.
• Score each tool using checklist provided
• Pass two completed tools to next group
  (1QR,,9OP).
• Score each tool using checklist provided
• Pass two completed tools to next group
  (1OP,,9MN).
• Score each tool using checklist provided
• Report final scores for each tool A,B,,R

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Interpretation

• Score
• gt90 Good Tool has no major ergonomic flaws.
• 75-90 Fair Lacks 1-2 important ergo features.
  May lack additional features that are important
  in some operating situations
• lt75 Poor Lacks multiple important design
  features.
• (Dababneh et al., 2004)

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Discussion Questions

• How useful is this formal evaluation approach?
• Might it inform the design of adaptations for
  disabled workers?
• What are its limitations? (E.g. internet/mail
  order evaluations)
• Can we internalize the technique through repeated
  application?
• Other comments/questions?

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References
Dababneh, Awwad, Lowe, Brian, Krieg, Ed, Kong,
Yong-Ku and Waters, Thomas(2004) 'Ergonomics A
Checklist for the Ergonomic Evaluation of
Nonpowered Hand Tools', Journal of Occupational
and Environmental Hygiene, 112, D135
D145 John R. Myers and Roger B. Trent Hand tool
injuries at work A surveillance perspective
Journal of Safety Research Volume 19, Issue 4,
Winter 1988, Pages 165-176.
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Poll Please complete, detach and return

• For each of the two statements below, underline
  the response that most closely reflects your
  present opinion
• From an injury risk reduction standpoint, this
  formal tool design evaluation approach is likely
  to be
• Ineffectual
• Neither ineffectual nor effective
• Undecided
• Effective
• I am likely to use this approach when selecting
  or specifying tools in the future
• Disagree
• Neither disagree nor agree
• Undecided
• Agree
• It will help when designing tool adaptations for
  disabled workers
• Disagree
• Neither disagree nor agree
• Undecided
• Agree