Experimental analysis of user forces by test bench and manual hammer drill experiments with regard to vibrations and productivity

The user's forces have great influences on the load and on the drilling process of hammer drills. Hence, these influences must be known in product development for reproducible testing on test benches. Furthermore, manufacturers focus on developing hammer drills, which improve productivity and force-efficiency during application. Therefore, the aim of this study is to investigate the influences of the forces exerted by the user on a hammer drill when drilling in concrete. For this purpose, the applied forces and the resulting vibrations of three users drilling in different directions at different force levels were analyzed and compared with an automated test bench, which is equipped with a hand-arm model. It can be shown that the commercially available hand-arm model cannot reproduce the vibration properties of the subjects. Further findings from the experiment are that the subjects applied lateral forces, which do not occur adequately on the test bench. The feed force has an influence on the rate of penetration and there is a force-efficient operating point, which differs from the highest rate of penetration. The results indicate that further investigations need to be carried out to analyze user influences on a broader scale. •The feed force has an influence on penetration rate in spatial drilling directions.•A force-efficient operating point differs from the highest penetration rate.•In manual tests lateral forces occur which must be modeled on test benches.•The commercially available hand-arm model does not simulate user characteristics.