Grinding fluids perform several important functions during the grinding process including chip removal from the grinding area, heat removal, and protection from chemical reactions during the grinding process.
Oil-based grinding fluids provide the best performance when using CBN wheels. Water-based grinding fluids are not quite as suitable for CBN grinding applications for a number of reasons but primarily due to accelerated breakdown of CBN particles and hence a shortening of the wheel life. The exposed surface of CBN crystals will oxidize even in oil-based grinding fluids at high temperature..but oil based coolant is still more suitable than water based.
Oil-based grinding fluid provides good lubrication, but poor cooling. The use of oil reduces the friction in the grinding zone and will result in lower grinding power. The boiling temperature for oil coolant is 3OOF, which decreases the occurrence of the oil film boiling. Oil-based coolant is excellent regarding the machine component maintenance, yet there are many environmental dangers. Also, filterability is much more difficult. The need for lubricity is not as crucial when grinding with diamond as it is when grinding with the CBN.