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Because of effective machining operations with a very small amount of cutting fluids, near-dry machining attracts increasing attentions for environmental and economical benefits. MQL machining has so far been recognized as the most representative near-dry method and it is highly successful in machining of most ordinary steels. Recent concern for environmentally friendly manufacturing further encourages the attempts at applying near-dry operations to machining of difficult-to-cut materials. Since titanium alloys are typical difficult-to-cut materials, this paper investigates the cutting performance of various near-dry methods in turning of a titanium alloy from the view point of elongating the tool life. Those near-dry operations include supply methods of regular MQL mist, coolant mist and hybrid mists, where the coolant mist is atomized water-soluble cutting fluid and hybrid mists are the mixture of MQL and coolant mists. The regular MQL operation provided longer tool life than that of dry machining. In addition, compared with MQL machining, the hybrid mist operations could further extend tool life and, in particular, the single coolant mist operations demonstrated the possibility of making the tool life longer than that of ordinary wet machining with flood cutting fluid supply.

Near-dry machining attracts increasing attentions for environmental and economical benefits, and MQL machining has been recognized as the most representative near-dry method. It is highly successful in machining of most ordinary steels, and synthetic biodegradable polyol esters play a significant role as an effective cutting fluid with a very small amount. Recent concern for environmentally friendly manufacturing further encourages the attempts at applying near-dry operations to machining of difficult-to-cut materials. Since titanium alloys are typical difficult-to-cut materials, this paper investigates the cutting performance of various near-dry methods in turning of a titanium alloy from the view point of elongating the tool life. Those near-dry methods include regular MQL and hybrid mist supply operations, where the hybrid mist is a mixture of MQL mist and coolant mist which is atomized water-soluble cutting fluid. The regular MQL operation provided considerably long tool life compared with that of dry machining and the hybrid mist operation showed the possibility of making the tool life longer. The cutting performance was largely influenced by the type of MQL lubricants. In particular, a synthetic polyol ester lubricant having low viscosity indicated the successful cutting performance when it was combined with the coolant mist supply in the hybrid mist application.

In minimal quantity lubrication (MQL) machining of aluminum alloys, since they have highly adhesive characteristics, more effective lubrication is necessary. This study therefore proposes that oxygen-including compounds, such as esters, alcohols and acids, are considered to be a potential MQL lubricant. The experimental investigations have shown the cutting performance of those oxygen-including compounds has greatly been influenced by their chemical structures. Some of them have been able to provide the successful cutting performance as a MQL cutting fluid and, in particular, specific alcohols have demonstrated the superior anti-adhesive characteristics in MQL end milling.

MQL technique has been recognized as the most representative method of environmentally friendly near-dry machining. In machining of aluminum and its alloys, since they have highly adhesive characteristics, effective lubrication is often necessary and MQL machining sometimes finds difficulty. This paper therefore investigates the lubricating action of MQL media with various compositions in machining of aluminum. Detailed examination regarding the contents of carrier gases has demonstrated oxygen leads to the low cutting performance and its concentration in carrier gases has to be kept below the level between 1% and 10% to attain successful MQL machining of aluminum. Further, increasing the amount of MQL lubricant supply by boosting the air pressure is the efficient and convenient way to make MQL drilling of aluminum satisfactory.