Study on Tool Wear and Cutting Torque of Gun Drill

The force model of gun drill was put forward. It was found that the torque was sensitive to wear and carried the information of the status of wear stage. Moreover, friction between wear pad and work piece was the main source of torque. The experiment applied in studying the correlation between torque and wear has been performed on gun drill with and without TiAlN coating for machining steel S48CSiV with minimum quantity lubrication (MQL). The torque was increasing responding to the increasing wear of gun drill. The TiAlN coating delayed the wear rate and decreased the torque in the initial wear and gradual wear stage of the coated gun drill. The spallation of coating always led to the premature failure of coated gun drill and the spallation appeared if the rubbing and sliding force generated in the interface between the wear pad and the newly surface of work piece after drilling obtained a higher value than the coating’s adhered strength to carbide substrate materials.