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In this study, Ti-6Al-4V alloy was machined at high cutting speed of 200 m/min, and the tool wear progress and the cutting mechanics were experimentally investigated in order to clarify an effective cooling method. The cooling method used in this study was five kinds of cooling method, namely dry, wet, oil-mist, water-mist and oil-water-mixed. The mist was supplied by MQL device. The quantity of water and oil can be regulated in this device. The tool wear was measured in each experimental condition. And the relation between the tool wear and the chip length was investigated. The results obtained as follows: In the cutting with the TiAlN coated cemented carbide tools at the cutting speed 200 m/min, the wear progress in the oil mist cutting and oil-water-mixed cutting were slower than that in dry and wet cutting. Adhesion of the chips on the tool was prevented by the lubricating oil-mist and the air compressed blew the chips. And the proper amount of the water in the oil-water-mixed mist was important condition. Tool wear was progressed easily because the thermal shock in case of the wet condition and the large quantity of the oil-water-mixed mist conditions. The connection of the chips got longer as the tool wear was increasing.

The high speed milling of Ti-6A-4V was investigated in order to clarify the efficiency of MQL and PVD coated tool. Cutting speed was very high 200m/min. TiAlN, TiCN, TiN, DLC and non-coated tools were used. Cooling methods were dry, wet and MQL (15mL/h). In wet conditions, flaking was observed on all tools by thermal crack. So, tool life was very short on every tool. However the flaking did not occur in the dry and MQL cutting. And the tool life in the dry cutting was longer than that in the wet cutting. Tool life of PVD coated tools were longer than that of the non-coated tools in dry and MQL cutting. TiCN coated tool was long tool life compare to the other coated tools in dry cutting. The tool life in MQL method was longer than dry method except for TiCN coated tool. The wear progress of PVD tool was similar in MQL cutting. The tool life of DLC and TiCN coated tool was almost same in MQL method. And the longest tool life was TiN coated tool in MQL. Furthermore, cutting temperature was measured for each tool in dry cutting. Cutting temperature of TiN coated tool was lower than that of TiAlN and non-coated tool. And the cutting temperature of DLC and TiCN were lower than the other coated tools.

This paper presents tool life (flank wear) and crater wear of four kinds of coated high-speed steel tools and finished surface roughness in hobbing under the conditions of considering environment. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. As a consequence, the following results were obtained. (1) Under the condition of 1-thread hob, TiN- and AlCrSiN-coated tools showed the longest tool life among the four kinds of coated tools in dry and with MQL system. Under the condition of 3-thread hob, TiSiN-coated tool is effective in dry, and TiAlN- and AlCrSiN-coated tools are suitable with MQL system. (2) The crater wear of TiN-coated tool is smallest in other coated tools tested both in dry and with MQL system under the condition of 1-thread hob. TiAlN-, TiSiN- and AlCrSiN-coated tools are effective, and it was suggested that the crater wear is protected by the deposited metal under the condition of 3-thread hob. (3) The finished surface roughness, which was obtained with almost of coated tools tested at the end of cutting with MQL system both under the conditions of 1- and 3-thead hobs, is smaller than that obtained by dry. (4) From the viewpoints of tool life, crater wear and finished surface roughness, AlCrSiN-coated tool is suitable for hobbing with MQL system.

This paper deals with the effect of minimal quantity lubrication (MQL) on tool life (flank wear), crater wear of various coated high-speed steel tools and finished surface roughness in hobbing. Experiments were conducted by simulation hobbing by fly tool cutting on a milling machine. The results are summarized as follows. (1) When changing the kinds of coating films, a TiAlN-coated tool showed the longest tool life. Tool lives of almost of the tested coated tools obtained with MQL system are longer than those obtained by dry cutting, and the wear reduction effect by MQL was recognized. Especially, an AlCrSiN-coated tool showed the tool life more than twice compared with dry cutting. (2) It is assumed that the crater wear is caused by the delamination of the coting film, and the crater wear in the case of MQL occurs earlier than that in dry cutting. Both in dry cutting and MQL, the crater wear does not appear on the AlCrSiN-coated tool, which is effective for the crater wear. (3) In all of tested coated tools, the finished surface roughness obtained with MQL is smaller than that obtained by dry cutting. When using TiAlN- and AlCrSiN-coated tools, the surface roughness reduction effect by MQL is large. The TiAlN-coated tool showed the smallest surface roughness of the four kinds of coated tools. (4) From the viewpoints of tool life, crater wear and finished surface roughness, TiAlN- and AlCrSiN-coated tools are suitable for MQL system.