Direct and Independent Measurement of Flank-Face and Rake-Face Temperatures Using Electrically Insulating Layer Combined with Tool–Workpiece Thermocouple Method

The cutting temperature is an important aspect of the cutting process, and various methods have been devised to measure it. However, most previous studies have focused on the rake-face temperature since the highest temperature is generally observed near the cutting edge on the rake face. On the other hand, tool life and surface quality are strongly related to flank wear; therefore, the flank-face temperature is also of considerable practical importance. This study proposes a method that combines an electrically insulating layer with the tool–workpiece thermocouple method. By placing the insulating layer on the rake face or flank face, the flank-face or rake-face temperature can be measured directly and independently. The proposed method is first validated in the cutting of brass by comparing the rake-face, flank-face, and dual-face temperatures. The method is then applied to the cutting of medium carbon steel to investigate the evolution of the flank-face temperature during flank-wear progression. The results support the feasibility of directly and independently measuring the apparent average temperatures of the flank and rake faces and demonstrate that the measured flank-face temperature increases with flank wear.