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Showing 4 results for Hand Tools
The effect of non-powered hand tools' diameter on comfort and maximum hand torque
Mohammad Sadegh Sohrabi,
Volume 3, Issue 2 (9-2015)
Abstract

Introduction: The weak design of hand tools and their disharmony with the user's physical features comprise a major risk factor for upper limb musculoskeletal disorders. Hand-tool related injuries comprise almost 9% of all work-related injuries. The present study was conducted to examine the effect of hand tools' diameter on comfort and maximum hand torque and to estimate the optimal diameter for hand tools.

Methods: Participants included 6 men and 6 women with a mean age of 24.7 and a standard deviation of age of 5.84 years. Participants started to load and rotate the grip of 7 hand tools with different diameters with all their power and using a self-made tool for measuring the torque. The test duration, maximum torque and comfort level of the tool grip was then measured and the data obtained were analyzed using the ANOVA and the t-test.

Findings: The mean maximum torque value obtained was 1.88 (SD=0.95) newton meter, the time taken to reach the maximum torque was 13.96 (SD=9.03) seconds and the mean comfort level was 3.27 (SD=1.48) at a scale from 1 to 7. There was a significant difference between the maximum torque generated in the group of men and the group of women (p<0.001). The mean maximum torque obtained was 3.034 newton meter and the mean maximum comfort level was 4.67, achieved with a grip diameter of 38 mm.

Conclusion: The optimal hand tool diameter recommended for maximum user comfort and torque is 38 mm.


Ergonomic Design and Evaluation of Fabric Cutting Scissors with Regard to Pinch Force and Wrist Posture
Soudabeh Asadollahi, Iman Dianat, Moein Nedaei,
Volume 5, Issue 2 (9-2017)
Abstract
Introduction: Scissors are essential tools in different occupations including sewing and clothes making. Improper design of fabric cutting scissors can lead to the development of musculoskeletal symptoms among users. The aim of this study was to evaluate pinch force and wrist posture while working with three designs of sewing scissors and a traditional sewing scissors.
Methods: The first model of the scissor had a bent-handle (to improve wrist posture), the second model had a thumb-ring that was located closer to the pivot (to reduce thumb’s abducted position and range of movement), and the original oval ring in the third model was changed to a hook-shaped handle (to reduce hand and finger discomfort). Pinch force was measured using a pinch gauge and wrist posture was measured in two anatomical planes including flexion/extension and ulnar/radial deviation using the observational method.
Results: The results showed significant effects of scissors' design on pinch force exertions (P < 0.01) and ulnar/radial deviation of the wrist (P < 0.001). The lowest level of pinch force decrement between pre- and post-pinch force measurements was recorded for the second model (2.4%), while the highest level was recorded for the traditional model (7%). More neutral wrist postures in ulnar/radial direction (83%) were recorded for the first model compared to the other designs.
Conclusions: The second scissors, which was designed to reduce thumb’s range of motion and abduction, showed some improvement in pinch force compared to the traditional model.

Relationship Between Usability Scale Score and Dimensional Properties and Weight of Socket Wrench in a Simulated Task
Mahnaz Ahmadlu, Mostafa Pouyakian, Mohammad Ranjbarian, Soheila Khodakarim,
Volume 7, Issue 2 (9-2019)
Abstract

Background and Objectives: There are various models of socket wrench in the market varying in the length and diameter of handle and weight. Each of these features alone can modify the force applied by the hand and affect how comfortable the user is. The purpose of this study was to investigate the relationship between dimensional properties and weight of several models of socket wrench with their usability index score.  
Methods: 58 male technicians from maintenance units of Shahid Beheshti University of Medical Sciences performed the task of opening 12 bolts with 8 N/m of torque using 6 models of socket wrench with different physical properties. The sample size was selected based on proposed figures for usability studies.  The System Usability Index (SUS) validated questionnaire was used to determine the usability score of each model after the experiment. The study was conducted in 2017. SPSS 21 was used for data analysis.
Results: The results showed that there was a significant relationship between usability index score and dimensional properties and weight of wrenches (P<0.001). Wrench models with longer handle and diameter size close to optimum range of diameter of hand tools for male users had a higher usability score, and participants reported a better test experience with these models.
Conclusion: Using the System Usability Index (SUS Questionnaire) to measure the quality of human-centered design of hand tools is a good way to evaluate and select the hand tools that are widely used by technical staff. The results of this study are valid for short-term applications of wrenches. However, for long time activities, epidemiological and physiological evidences such as EMG should also be used.


Psychometric Properties of the Persian Version of the Comfort Questionnaire for Hand tools (CQH)
Azam Maleki-Ghahfarokhi, Iman Dianat, Mohammad Asghari Jafarabadi, Mohamad Parnianpour, Mahmood-Reza Azghani, Maryam Khosravifar, Sina Samadi,
Volume 10, Issue 1 (7-2022)
Abstract
Objectives: The comfort questionnaire for hand tools (CQH) is a subjective measure for exploring the starting points for improving hand tool design. This study aimed to investigate the psychometric properties of the Farsi version of the CQH.
Methods: In this cross-sectional study, which was conducted among 163 university students, the 17-question CQH was translated into Farsi with a translation back-translation procedure. Content validity was assessed by a panel of 10 experts. Exploratory Factor Analysis (EFA) was applied for determining construct validity. Cronbach’s alpha and Intraclass Correlation Coefficient (ICC) were used for assessing internal consistency and test-retest reliability, respectively. Ceiling and floor effects were also estimated for evaluating the feasibility of the measure.
Results: The CQH showed good content validity. Content validity index (CVI) ranged from 0.80 to 1.00 and Content Validity Ratio (CVR) ranged 0.62-1.00. EFA led to extraction of two factors from the data. The first one was mostly related to functionality and physical interaction and the second one, was generally about adverse body effects. The Cronbach’s alpha was 0.74 and test-retest reliability was 0.74 (95% CI = 0.58 to 0.86) which both were satisfactory. There were no (0%) ceiling and floor effects.
Conclusion: The Farsi version of CQH is an acceptable and useful instrument for evaluating hand tools comfort.

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