Cutting fluids are used within metal machines. Cutting oils fulfill a variety of different purposes for metal machines; they help improve performance and extend the life expectancy of machines and also help with practical matters such as flushing away cutting and improve the surface flow on the machines. There are four different primary types of cutting fluids that are used on metal machinery.

#1 Synthetic Fluids

Synthetic fluids do not contain any petroleum nor do they contain any mineral oil as well. Synthetic fluids are made out of both organic and inorganic alkaline compounds. There are generally additional additives included in the fluid to prevent corrosion. Synthetic fluids excel at cooling down equipment. They are also generally diluted with water before being used. Synthetic cutting fluids are generally one of the more expensive cutting fluids on the market. 

#2 Straight Oils

Straight oils are generally not diluted and are used in their natural form. Straight oils have mineral or petroleum bases. They also generally contain other elements to make them more lubricating, such as vegetable oils and fats. They may also have additional additives that help machines maintain their pressure. Pressure related additives generally include things such as phosphorus and Chlorine.  Straight oils are best for machines that need lubrication and perform most poorly at cooling down equipment. 

#3 Soluble Oil Fluids

Soluble oil fluids are one of the most affordable cutting fluids. As one of the most affordable cutting fluids, soluble oils are also one of the most widely used cutting fluids. Soluble oil fluids are often used in industrial settings.  Soluble oil fluids have a mineral oil base and are missed with an emulsifier. This is used to create a stable emulsion. Soluble oil fluids are generally diluted. They work best at both transferring heat within machines and at lubricating, which is another reason why soluble oil fluids are so popular for industrial uses.

#4 Semi-synthetic Fluids

Semi-synthetic fluids are a hybrid cutting fluid. They are a combination of synthetic and soluble oil fluids, which means that they are both able to cool down equipment, transfer heat, and provide solid lubrication properties to the machines that they are used on. Semi-synthetic fluids also fall right in the middle price wise, not being as expensive as synthetic fluids nor as affordable as soluble oils. They are a great middle-ground cutting fluid because of the price-point and the things that semi-synthetic fluid can assist metal machines with.