In this paper, we focus on the temperature sensing and data collection of milling tools during the machining process. The collected data is visualized in real-time dynamic charts using the ThingSpeak platform. In case of temperature abnormalities, users are notified via LINE for inspection or tool replacement. The control system is implemented using a flexible printed circuit board embedded within the concentric cylinder of the milling cutter’s handle. The Arduino programming language is used for programming, and temperature measurement is achieved through a K-type thermocouple module combined with an ESP32 microcontroller, utilizing Wi-Fi to transmit data to the ThingSpeak platform for real-time monitoring on computer screens. The system’s advantage lies in enabling users to monitor the temperature of milling tools, preventing tool dullness or damage, and improving machining accuracy by reducing the frequency of tool replacement. This system is particularly suitable for milling machines that use cutting fluid. Temperature abnormalities indicate a decrease in cutting capability owing to tool dullness, resulting in increased heat generation during cutting or the insufficient cooling capacity of the cutting fluid with respect to the heat generated during cutting. Such alerts allow timely inspection or tool replacement. However, most modern milling machines come equipped with their own monitoring systems for tool wear and temperature. Hence, in this paper, we primarily focus on monitoring milling tool temperature. The upper-temperature limit for alerting is set at 290 °C on the basis of the expected hardness of tungsten carbide, which is suitable for machining up to this temperature. Currently, a warning temperature of 200 °C is used. This enables users to determine the condition of the tool during operation, ensuring safer use and facilitating better quality control and industrial safety for manufacturers.