Fundamental Research on Hobbing with Minimal Quantity Lubrication of Cutting Oil

In this paper, we investigate the effect of cutting speed on flank wear, crater wear and finished surface roughness during hobbing using an uncoated tool, and TiN- and (Al, Ti)N- coated tools with a minimal quantity lubrication (MQL) system. The experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results helped clarify the following points. (1) With the uncoated tool and the TiN-coated tool, the flank wear increases upon increasing in the cutting speed from 47m/min to 86m/min. Conversely, flank wear decreases at the higher speed of 117m/min. It was impossible to cut at 159m/min owing to the failure of the cutting edge. With the (Al, Ti)N-coated tool, the flank wear showed nearly the same small value, irrespective of cutting speed. (2) The cutting speed also has a large effect on crater wear, particularly for the TiN-and (Al, Ti)N-coated tools. The cutting speed of 117m/min is suitable for decreasing crater wear. (3) The finished surface roughness is small for all the tools used in this test for cutting speeds less than 86m/min, after which it becomes large because of the adhesion of deposited metal at cutting speeds more than 117m/min. When using the TiN- and (Al, Ti)N-coated tools, there is a critical cutting groove length, at which the surface roughness decreases rapidly.