Performance Analysis of Professional Sewing Scissors Using the 'So-Hizukuri' Forging Process

摘要

Scissors have been around since the ancient times as a useful tool. They come in many varieties and serve just as many purposes. This team of researchers completed an earlier study, investigating the secret to the sharpness of Japanese sewing scissors. Japanese sewing scissors can be traced back 160 years ago to the time Commodore Perry arrived in Uraga, Japan, then perfected over time by the grandfather of Japanese scissors, Yakichi Yoshida, to fit Japanese hands. This forging process came to be known as "so-hizukuri." Today, this traditional technology is known and handed down to just a handful of craftsmen. Our research team wanted to know why this process created scissors that were so sharp, so we began measuring each ridge in the blades of the scissors. Results showed that scissors forged under the so-hizukuri process had blades that curved between 0-150 micrometers in width. When, in use on a fabric, the two blades intersect along the curve, generating greater friction that translates into sharper blades. We also learned that when the two blades intersect, other parts of the blades do not touch each other. In this study, we looked at what happens to the user of the scissors and the fabric at the very moment the sharp blades of so-hizukuri forged scissors cut into the fabric. We armed a tailor - someone who is an expert scissor handler - with two different pairs of scissors: one that's so-hizukuri forged, and another that's cheap and sold in discount stores. We then had the tailor cut the same fabric using the same method but with two different scissors and recorded the process using a high-speed camera. We analyzed the footage. Additionally, we observed the surface of the fabric cut by the two scissors under an optical microscope. We found clear differences in the user's movements and the scissors' effects on the fabric, which shall be elaborated upon here.