A representative cutting process in machining is the removal of unnecessary parts using a tool with a higher hardness than the material to be machined and machining it into a desired shape. To improve productivity through cutting, increasing the speed of the feed system through the tool path setting and control system and reducing defects occurring in the tool during work are important. In this study, the flow fields inside and outside the nozzle were designed, and a numerical analysis was conducted to develop the core shape inside the fluid supply nozzle to improve productivity through the nozzle and increase tool life. A diamond-shaped pattern was added to the nozzle core, and the operating characteristics were compared based on the presence of the pattern. In addition, the operating characteristics at various flow rates were compared in the presence of the nozzle core pattern. Numerical analysis confirmed that the diamond-shaped pattern could increase the life of the tool and reduce power consumption by reducing the differential pressure and increasing the nozzle outlet velocity.