Durability of Cutting Performance of a Knife and Micro-Structural Change of a Knife Edge

Abstract

The tested knife material here is mainly SUS420J2 (a kind of stainless steel). This kind of knife is very popular for daily use. From SEM observation of the initial state of the knife-edge tip after the burr removal treatment, we find either some burr and/or a micro-groove, or no burr and no micro-groove along the edge-tip. In order to abrade intentionally, the edge of a knife is repeatedly rubbed perpendicularly to the surface of a Japanese cypress woodblock using the durability-testing machine. During this rubbing process, the abrasion and/or crushing of the edge tip are observed by SEM in detail. The frictional load between the knife-edge and the woodblock is measured. Using the cutting-test machine, the cutting performance of the abraded knives is evaluated by the number of cut pieces of paper. It is discovered that the groove evolves and grows on the edge tip with abrading operation. Moreover, it is concluded that both micro-sidewalls of the groove play a role as cutting edges (i. e., the secondary edge) and this secondary edge and the groove width govern the durability of cutting performance of the knife. Especially the groove width governs it most. These conclusions are also valid for the knives made of other materials such as SUS410 and SUP10.