ByMartin Supply •
Pros and Cons of Oil-Based Coolant
You have several options for selecting a coolant in CNC machining. About 85% percent of machine shops today use a water-based fluid in their applications. These include soluble oils, synthetics, and semi synthetics. However, in precision machining applications, an oil-based coolant is a better option.
What are oil-based coolants?
Oil-based coolants do not contain water. They are also known as cutting oil, petroleum, vegetable, or mineral-based fluids. These fluids are used in light ferrous and non-ferrous machining applications. In more heavy-duty applications these coolants may contain wetting agents, up to 20 percent fatty oils, and extreme pressure (EP) additives such as chlorine, sulfur, or phosphorous compounds. These additives help improve lubrication and coat the tool, as well as guard against microscopic welding which can lead to tool breakage and rough finishes.
An advantage of using oil as a coolant is the “cushioning” effect it has between the workpiece and cutting tool. Oil helps create high-quality surface finishes and prolongs the life of the tool. Oil-based coolants tend to be the coolant of choice for crush grinding, deep-hole drilling, severe broaching and tapping and for machining difficult-to-cut metals such as certain stainless steels, superalloys, and titanium. Additionally, these coolants are easy to maintain and less likely to cause problems if misused. They also provide rust protection, increase sump life and resist rancidity due to the lack of water for bacteria to grow.
Oil-based coolants do have some disadvantages. Their heat dissipation ability is lacking, and they can create a mist or smoke that can be harmful to shop operators. This can increase the risk of fire, making it important to have proper fire suppression and ventilation systems in place. Oil-based coolants tend to messy, leaving an oily film on workpieces and tools, making cleanup more difficult and requiring the use of cleaning solvents.
The table below shows coolant recommendations based on the machining processes and materials being machined.