Emulsion is made by diluting emulsified oil with water. Emulsified oil is a mixture of mineral oil, emulsifiers, and additives, diluted with 95% to 98% water to form a milky white or semi transparent emulsion.

The main component of cutting oil is mineral oil, and there are also small amounts that use animal and vegetable oil or composite oil. Pure mineral oil cannot form a strong lubricating film on the friction interface, and the lubrication effect is average. In practical use, oil-based additives, polar additives, and rust inhibitors are often added to improve their lubrication and rust prevention performance.