A study of powered hand tools. Final report on CEC Contract 7247/12/009

The overall objective of the project was to apply ergonomic principles to the design of powered hand tools used in the coalmining industry, with the aim of reducing any accidents and physical stress associated with their use. In order to achieve this objective, tools commonly used in the mining industry were evaluated against ergonomic criteria, the effects of hand-arm vibration from tools on manual dexterity subsequent to tool use were studied, and a theoretical assessment was made of methods of using man-generated power as a power source for driving powered hand tools.A survey of powered hand tool usage in five National Coal Board Areas identifed five major categories or ‘families’ of tools, having functions and ergonomic characteristics in common, which had wide current and potential utility in the mining industry. Ergonomic limitations were found in design and operation of all of these tools.A review of the literature on powered hand, tool design revealed the lack of an integrated set of ergonomic criteria based on consideration of the powered hand tool as a man-machine system. We have therefore derived such criteria from relevant recommendations in the literature, adapted those for comparable equipment and tasks, or established criteria by experiment. As part of the latter, an investigation of the effects of tool vibration on subsequent manual dexterity showed that tool operation could produce a temporary reduction in vibration sensitivity at the fingertip (but no noticeable effect on tactile sensation or dexterity), and that this was unlikely to have any practical significance in subsequent manual tasks.None of the tools evaluated was completely satisfactory when compared with ergonomic criteria. Ergonomic limitations identified in the tool usage survey were, in general, confirmed by the results of the evaluations of representative tools, the main problems being associated with handle design,weight, balance, noise output, training in tool operation, and hand-arm vibration output.Although a man-generated power storage and transmission device was found to be theoretically feasible, it would have required considerable effort for very limited useful output, and was not considered viable for normal coalmining operations.In conclusion, ergonomic criteria were developed for tool evaluations which could be applied to most tools used in the industry and could identify those likely to affect health, safety and productivity. These criteria should form the basis of ergonomic principles for tool design and operation.Although we are not aware of any clinical evidence of vibration-induced white finger in the UK coalmining industry, vibration levels and exposure periods need to be kept under review, since some tools are likely to exceed ISO hand-arm vibration criteria if used for prolonged periods.