The usability and ergonomics of axes

The contact length parameter as a geometric factor for user-centered design of pistol grip geometries of power tools

In this study the geometric parameter of the contact length is introduced, which intends to combine force exertion and perceived handle comfort in an anthropometric length in order to determine an optimal handle circumference. To prove suitability of the approach, 31 subjects were determined and correlations to handle circumferences with the highest finger forces and highest rated comfort were investigated. For all fingers, medium correlations were found among the contact lengths and the circumferences determined with maximum force (p < 0.001, r_index = 0.348, r_middle = 0.419, r_ring = 0.374 and r_little = 0.337) with high accordance of median values. Weak to moderate correlations were found between circumferences with maximum comfort and the contact lengths (p < 0.001, r_index = 0.150, r_middle = 0.265, r_ring = 0.174). Using finger-specific proportionality factors, the contact lengths can be determined directly from the hand lengths, which enables great benefits for user-centered design.

Objective usability evaluation of drywall screwdriver under consideration of the user experience

During validation of power tools, one objective is to determine the usability of the device for several applications. A common way to gain this user knowledge is to carry out tests under laboratory conditions with non-professional craftsmen, whereby a non-professional user does not work and evaluate a power tool similarly to a professional. Therefore an experimental study was conducted to investigate the possibility of training non-professionals in the professional working methods and evaluation of relevant key criteria for drywall screwdrivers. 39 subjects were divided into three groups and trained in the professional use of a drywall screwdriver. Results indicate that targeted training significantly improves the professional way of working (professional hand position p = 0.000, β = -0.764) and evaluation (testing of mass distribution p = 0.000, β = -0.731) of a drywall screwdriver. The gained knowledge can be used for the implementation of objective usability test-environments to derive specific and differentiated user-centered development potentials under laboratory conditions.

Non-powered hand tool improvement research for prevention of work-related problems: a review

PURPOSE

In lower-middle-income countries, most of the work is performed manually using non-ergonomic hand tools which results in work-related health problems. Using hand tools designed in line with ergonomic principles may play an important role in reducing work-related health concerns significantly.

METHODS

Scientific databases (PubMed, EBSCOhost) and e-publishers were searched for articles from 1985 to 2015 using the following keywords: 'hand tool', 'ergonomics', 'usability' and 'design'. After applying selection criteria to 614 articles, 58 articles related to the physical design of hand tools were selected.

RESULTS

Seventeen articles were related to hand tool improvement in the manufacturing sector. Musculoskeletal disorders were found to be the most frequently occurring work-related health problems. Most of the articles focused on product and qualitative variables for improvement in hand tools, while few articles considered human and task variables.

CONCLUSIONS

Literature shows that hand tool improvement studies have been given less importance in low-income and lower-middle-income countries. However, some work of significance is reported in the agriculture sectors of these countries. Hence, it is concluded that ergonomic intervention in hand tools is much needed for those industries which employ traditional methods of working.

Effects of tool handle dimension and workpiece orientation and size on wrist ulnar/radial torque strength, usability and discomfort in a wrench task

The effects of tool handle dimension (three modified designs of wrenches with 30-50 mm diameter cylindrical handles and traditional design with rectangular cross-sectional (5 mm × 25 mm) handle), workpiece orientation (vertical/horizontal) and workpiece size (small/large) as well as user's hand size on wrist ulnar/radial (U/R) torque strength, usability and discomfort, and also the relationship between these variables were evaluated in a maximum torque task using wrenches. The highest and lowest levels of maximal wrist U/R torque strength were recorded for the 30 mm diameter handle and traditional wrench design, respectively. The prototype handle with 30 mm diameter, together with 40 mm diameter handle, was also better than other designs as they received higher usability ratings and caused less discomfort. The mean wrist torque strength exerted on a vertically oriented workpiece (in the sagittal plane) was 23.8% higher than that exerted on a horizontally oriented one (in the transverse plane). The user's hand size had no effect on torque exertions. The wrist torque strength and usability were negatively correlated with hand and finger discomfort ratings. The results are also discussed in terms of their implications for hand tool and workstation configuration in torque tasks involving wrenches.