This paper deals with the effect of quantity of oil supply in turning with minimal quantity lubrication (MQL) of cutting oil, compared with dry cutting, in terms of tool wear and finished surface roughness when changing the feed rates and the cutting speeds. The results obtained are summarized as follows. (1) At the feed rate of 0.2 mm/rev, the MQL system (the quantity of oil supply of 15 mL/min) compared with the dry cutting is effective for the side flank boundary wear, VK1 when changing the cutting speed. When the quantity of oil supply was increased to 30 mL/min, the VK1 becomes smaller which prolonged the tool life. The MQL system decreased the side flank wear, VB, but it increased the front flank boundary wear, VK2. (2) In the case of feed rate of 0.4 mm/rev, the MQL system also showed the reduction effect of the VK1 and VB when changing the cutting speed. Increase in the quantity of oil supply resulted the longer tool life. (3) The finished surface roughness obtained with the MQL system is smaller than that obtained with the dry cutting, and increasing in the quantity of oil supply showed a tendency of the better finished surface roughness.
