Evaluation of bent-handled files

The file is a non-powered hand tool extensively used in the manufacturing i ndustry. However, the conventional flat file with a straight handle frequen tly causes excessive ulnar deviation of the user's wrist. Therefore, repeti tive and long-time use of the file likely inflicts the user with cumulative trauma disorders (CTDs) at the upper extremities, in particular carpal tun nel syndrome (CTS). In this work, we present a novel bent-handled flat file , designed from an ergonomic perspective as an improvement over the convent ional file with a straight handle. This novel re-designed product was teste d to verify its effectiveness. Five criteria were tested: the subject's wor king posture (right arm), task efficiency (filings), task precision (flatne ss), 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 th e 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 prefer ences. The other two criteria, task efficiency and task precision, show no significant difference. The ergonomically friendly files (with the handles bent from 50 degrees to 70 degrees) ensure optimal use. The bent-handled fi le has the same function in filings and flatness as the straight-handled fi le. In particular, the 60 degrees file is excellent. The bent-handled flat file not only reduces cumulative trauma, but fulfills the requirements of t he operatives.