Hand Tool Selection and Design for Usability, Safety, and Health Robert Stuthridge B. Sc. , M. Sc. Ergonomist National Agr. Ability Project Purdue University West Lafayette, IN
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
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 • Mainly extremities affected. (Aghazadeh and Mital, 1987) – • 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
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: 1. 2. 3. 4. Construction Agriculture Manufacturing Mining
Hand Tools Defined Hand tools are: 1. Portable 2. Manipulable 3. Supported completely or partially by the hands. 4. Tool is applied to the raw material rather than vice versa (so the hand tool is usually the part that is moving).
Design features affecting risk 1. Handle design – grip/slip 2. Handle design – smooth/sharp edges 3. Handle design – insulated or not (electrical, cold) 4. Handle design – grip length 5. One-handle tools - cross sectional size of handle 6. One-handle tools - cross sectional shape of handle 7. Two-handle tools – grip span dimension 8. Angle of handle – wrist angle 9. Weight of tool 10. Handedness of tool – either hand 11. Handedness of tool – suitability for dominant hand 12. Tool design allows use of two hands 13. Color (visibility) of tool and its accessories in work environment
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.
Ergonomic checklist evaluation of hand tools
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)
Practical evaluation using checklist • Nine groups, 1 -9 • Each group evaluates two different tools labeled AB, CD, EF…QR etc. , for five minutes per tool. Group 1=AB, Group 2=CD, […], Group 9=QR. • Score each tool using checklist provided • Pass two completed tools to next group (1=QR, […], 9=OP). • Score each tool using checklist provided • Pass two completed tools to next group (1=OP, […], 9=MN). • Score each tool using checklist provided • Report final scores for each tool A, B, […], R
Interpretation • Score: • >90 = 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 • <75 = Poor: Lacks multiple important design features. (Dababneh et al. , 2004)
Discussion Questions 1. How useful is this formal evaluation approach? 2. Might it inform the design of adaptations for disabled workers? 3. What are its limitations? (E. g. internet/mail order evaluations) 4. Can we internalize the technique through repeated application? 5. Other comments/questions?
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, 1: 12, D 135 — D 145 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.
Poll – Please complete, detach and return • 1. 2. 3. 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 a) Ineffectual b) Neither ineffectual nor effective c) Undecided d) Effective I am likely to use this approach when selecting or specifying tools in the future a) Disagree b) Neither disagree nor agree c) Undecided d) Agree It will help when designing tool adaptations for disabled workers a) b) c) d) Disagree Neither disagree nor agree Undecided Agree
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