The straight oils are used in several types of operations. They are non-emulsifiable and are therefore used in an undiluted form. They are made up of petroleum oil with a base mineral. Most of them contain fats such as vegetable oils, fats and esters. In operations that are characterized by extreme pressure, phosphorous, chlorine and sulphur should be used. The straight oils are the cutting fluids that you will use when you want the best lubrication and poorest cooling combination.
The synthetic fluids contain no mineral base of petroleum products at all. They are formulate using alkaline organic and inorganic compounds together with additives that prevent corrosion. They are used in diluted form with concentrations ranging from 3% to 10%. They are the fluids that you will purchase when you want the best cooling performance.
The soluble oil fluids are in the form of emulsion when mixed with water. The base material and the emulsifiers assist in producing a stable emulsion which is used in diluted form. The concentration is the same as that of synthetic fluids. These cutting fluids are ideal in the production of good heat transfer and lubrication performance. They are used in the industries widely because they are the most affordable.
Lastly, the semisynthetic fluids are made of both soluble oil fluids and synthetic fluids. They therefore show characteristics of both types of fluids. Their cost and properties lie between those of the two fluids from which they are made.