A Numerical Investigation of Through-Tool Coolant Wetting Behaviour in Twist-Drilling

Supplying coolant through internal coolant channels is a common method of transporting large thermal loads away from the tool in twist-drill machining to increase tool life, aid chip evacuation and avoid catastrophic tool failure. In this work a finite element-based numerical model of the machining process is loosely coupled with a finite volumebased numerical method for predicting the distribution of coolant inside the borehole. These methods are employed to study the effect of channel position on cutting geometry lubrication and uses response surface models to show that all designs do not fully flood the borehole and that not all areas of the tool geometry are lubricated with coolant. Visual analysis of results show that coolant, for all designs, primarily lubricates the area between the cutting edge and the coolant hole exit, however depending on application requirements coolant channel positioning can be used to modify coolant supply to the axial rake, for chip evacuation or to the cutting edge for heat removal.