Characteristics of Cutting Performance for Japanese Sewing Scissors Made by the 'So-hizukuri' Forging Process

摘要

Scissors are commonly known as a tool that has been used since long ago. The X-shaped scissors currently commonly used in Japan date back to 160 years ago when Admiral Perry arrived in Uraga. Since that time Yakichi Yoshida, known as the originator of Japanese scissors, has made many reforms leading scissors to their present shape. His method is called "So-hizukuri", and today there is a very small number of artisans left who have inherited the So-hizukuri method. In previous research our research group investigated why sewing scissors made with the So-hizukuri method have a sharp cutting edge. The results showed that the surface of So-hizukuri method scissors blades have a curved surface with a difference of about 0-150 pm applied. It was suggested that the curved surface being applied causes the cutting power of the scissors to be focused onto the point where the two blades overlap when cutting cloth, leading to a sharp cutting edge. We also confirmed that when the two blades overlap the parts of the other blades are separated. In this research, we intend to extract characteristics of the So-hizukuri scissors with sharp cutting edges which were not clarified in the previous research. We had a tailor who is a specialist in handling scissors use new So-hizukuri sewing scissors and So-hizukuri sewing scissors which have been used for more than 20 years and which were both made by the same scissors artisan, and examined what effect this had on the operations of the person handling the scissors when cutting cloth. We had the person cut the same cloth under the same conditions using the same method, and recorded the process with a high-speed camera for analysis. The results showed a clear difference in the movements of the tailor when handling the So-hizukuri scissors and the cheap scissors, but no significant difference between the new So-hizukuri scissors and the So-hizukuri scissors which had been used for more than 20 years. We considered the reasons for this differ