Thanks for your questions, ratio of coolant oil absolutely depends on type of metal you cut on the machine, normally we check the concentration of coolant oil in water with an scale device (between 9 to 11 concentration is good). If concentration is less, it will cause of rusting in the machine and burn marks on the parts you cut on the machine. In US most of the customers use synthetic and semi synthetic coolant oil and which should be 5 to 15% coolant against water. But I would reccomend you to talk with your cutting tools provider they might have chart for specific metals.

For more details , please hit me up at: htakhi_usa@yahoo.com . I will provide you further assistance if required.

Thanks
Harvey