In order to avoid severe injuries in the event of entanglement accidents during hand-fed threshing by use of head-feeding combine harvesters, we studied here the conditions required for the machinery to be developed, while obtaining farmers’ opinions and attitudes toward hand-fed threshing and measurement of lifting force by female users. To satisfy these conditions, we developed prototypes additionally equipped with an opening function of either the threshing drum cover or the pinching rod, and thereby verified ability to allow users to pull out the entangled hand with ease. We completed research and development in 2013, and currently models of head-feeding combine harvesters equipped with this device are commercialized by four agricultural machinery manufacturers in Japan, spreading more than 6,000 units of 21 models.