Evaluation of bent-handled files

Abstract

The file is a non-powered hand tool extensively used in the manufacturing industry. However, the conventional flat file with a straight handle frequently causes excessive ulnar deviation of the user's wrist. Therefore, repetitive and long-time use of the file likely inflicts the user with cumulative trauma disorders (CTDs) at the upper extremities, in particular carpal tunnel syndrome (CTS). In this work, we present a novel bent-handled flat file, designed from an ergonomic perspective as an improvement over the conventional file with a straight handle. This novel re-designed product was tested to verify its effectiveness. Five criteria were tested: the subject's working posture (right arm), task efficiency (filings), task precision (flatness), the degree of right-arm fatigue (the decrease of grip force), and the subject's subjective preference ratings. According to our results, the bent-handled flat file is superior to the straight-handled flat file because the former can sustain the operator's forearm and hand in a neutral position, reduce the degree of right-arm fatigue, and adhere to the subject's preferences. The other two criteria, task efficiency and task precision, show no significant difference. The ergonomically friendly files (with the handles bent from 50° to 70°) ensure optimal use. The bent-handled file has the same function in filings and flatness as the straight-handled file. In particular, the 60° file is excellent. The bent-handled flat file not only reduces cumulative trauma, but fulfills the requirements of the operatives. Relevance to industry The flat file (tool) is extensively used in industry. Results in this study demonstrate that the bent-handled file (from 50° to 70°) not only maintains the operator's forearm and hand in a neutral position, but also reduces the extent of right-arm fatigue and satisfies the subject's preferences. It had no significant difference from the straight-handled file in filings and flatness evaluation. Therefore, the bent-handled flat file is safer than and equally efficient when compared with the conventionally used file