The cooling with cutting fluids is a complex process in manufacturing, since chemical, mechanical and thermal phenomena occur simultaneously. The experimental methods developed so far do not allow for a direct observation of the coolant flow during machining, which limits the understanding of the cooling mechanism. The main aim of this paper is the investigation of convective heat transfer between cutting fluid and the cutting zone as well as the heat flow distribution on the tool surface during the cutting process by means of a coupled FE-CFD simulation. The FE model calculates the heat generation under consideration of the experimentally validated punctual, transient tool temperature during the machining processes. Based on the result of the FE, the subsequent CFD simulation performs the calculation of the flow behavior and convective heat transfer. This method allows a detailed investigation of the temperature field in the cutting zone under consideration of the cutting fluid. The simulation returns spatially resolved heat transfer coefficients along the tool surface and provides first findings for an improvement of heat removal efficiency by changing the coolant supply parameters and the physical properties of the cutting fluid. The model parameters were validated by comparing the simulation results and the measured punctual tool temperature.