For centuries, metal cutting operations have relied heavily upon machine coolants as an effective lubricant. In the early years, fats, whale oils and even lard were acceptable forms of lubrication. However, as machine operations became more complex, special coolants were needed to meet the needs of the ever-changing metalworking industry.
Today, special blends of coolant are commonly used to enhance the mill’s performance. These types of milling machine coolant— synthetic and non-synthetic — are used in more than 90 percent of machine operations. The inner-workings of all milling machines consists of water, oil and water mix, synthetic coolant. The coolant is added to prevent machine rust and prevent heat buildup. Oil is often the lubricant of choice when heat transfer is critical part of the operation. Synthetic coolants are the better choice when grinding applications are in place.
This coolant has two categories: oil-based coolants and chemical coolants. Oil-based coolants consist of straight oils and soluble oils. Both have advantages and disadvantages. Straight oils consist of 100% petroleum. The oil is ideal for heavy cutting jobs. It completely coats the tool and provides a high level of lubrication. It also guards against microscopic welding in extreme conditions.
The use of straight oil also extends the life of the machine. Compounded straight oil is preferred for more severe operations like deep-hole drilling, difficult cutting jobs, and sump life extension. However, there are some drawbacks. Straight oils can increase the risk of fire. It can often create smoke and mist in the cutting environment. This can be especially hazardous when the are lacks ventilation. Due to the low-temperature and low-speed requirements, oily film can build up on the work parts. This can lead to the constant use of solvents for cleaning.
Soluble oils are also very good for lubrication. This oil is comprised of a 60% to 90% mix of some type of oil or emulsifier. Soluble oil improves cooling capabilities and can match the same operations handled by straight oils.
Soluble oils are known to have issues with rust control, contamination, and bacterial growth. These conditions can lead to costly maintenance in the long run. Other hazards include an unsafe work environment through product inhalation and slippery surfaces.
The chemical machine coolants and synthetics have been used in milling machines since the 1940s. While these products don’t contain petroleum oils, they do consist of chemical lubricants that creates a metalworking fluid.
These synthetic fluids are manufactured for lubricity, high cooling capacity, rust prevention, heat reduction, and corrosion prevention. These fluids are also non-smoking and have a much greater overall stability. They are also produced to reduce the problems with misting and foaming.
Some of the disadvantages of using synthetics include a number of health and safety concerns such dermatitis and bacterial infections from misting. The wettability of the synthetics can also lead to gummy buildup on machine parts. Synthetic fluids are also susceptible to cross-contamination from other machine fluids. It is advisable to closely monitor all machines that use synthetic fluids.