1. Straight Oil : Also called “cutting” or “neat” oils. This type is made up of mineral (petroleum), animal, marine, vegetable or synthetic oils. Today, the mineral oils are “severely solvent refined” or “severely hydrotreated”. These terms refer to refining processes that help reduce the amount of polynuclear aromatic hydrocarbons (PAHs). Straight oils are not diluted with water but other additives may be present.
2. Soluble Oil : This category contains 30 to 85 percent severely refined petroleum oils, as well as emulsifiers to disperse the oil in water.
3. Semi-synthetic fluids contain 5 to 30 percent severely refined petroleum oils,
30 to 50 percent water and a number of additives.
4. Synthetic fluids do not contain petroleum oils. Instead, they use detergent-like components and other additives to help “wet” the workpiece. |