Prediction of the convective heat transfer coefficient of cutting fluid in helical drills

Environmental, economical and social factors impose the elimination or reduction of the quantity of the cutting fluids used in the machining. This trend leads to a high temperature in the cutting zone. In drilling, when the cutting fluid is not supplied through the spindle, the tool tip suffers from high temperature, leading to rapid wear. In this case, the cooling of the drill tool body can contribute significantly removing the heat generated at the tool–chip interface. However, to effectively simulate the temperature at the tool tip, the effect of the cutting fluid on tool body must be known. Hence, the aim of this work was to determine the convective heat transfer coefficient of the cutting fluid on the complex body of a helical drill. In this regard, a special experimental setup is developed, allowing the drill to remain static while the coolant nozzle rotates around providing cutting fluid. A method is developed in order to determine the temperature on the drill surface as a function of the heat enters into the drill and the temperature measured at the tool base. Experiments are carried out varying coolant nozzle rotation speed and the cutting fluid flow rate. According to the results, the cutting fluid flow rate shows to have the most significant effect on the convective heat transfer coefficient.