Air–Oil Cooling Method for Turning of Hardened Material

The hard turning process, defined as single-point turning of materials harder than HR C 58, differs from conventional turning because of the hardness of the work materials and cutting tools needed in the process. In hard turning, tool life is very short, of the order of a few minutes, during which time the cutting tool is subjected to extreme stress and tempera-ture. In this regard, it is well known that CBN tools are well suited for this process despite their high cost. In this research, we studied the feasibility of using lower-cost cutting tools such as TiN coated tools. To this end, a new cooling system was designed using an air–oil method, which is based on the principle of air vortex flow, for reducing tool temperature. In this system, the temperature of air at the outlet is lowered by more than 20°C using pressurised air of 5 kgf cm −2 at the inlet. The cooled air ejected at the tip of the cutting tool lowers tool temperature, and reduces the wear of a TiN coated tool to give 30% of CBN tool life with respect to the same cutting length.