Some machine shops buy a certain coolant because the manufacturer offers the absolute lowest price per gallon. Others buy a coolant because the brand is advertised as extending tool and/or sump life. And some coolant is chosen only after a salesman has looked at your operation, assessed your needs, and made an appropriate recommendation.
How do you buy coolant? A company that has a central coolant system made of untreated concrete buried eight feet underground will not be buying a coolant that is designed to last a year or more because this “high-end” coolant is not the right coolant for the application. Even a “super” coolant would have a difficult time in this environment.
Your coolant sales professional should be able to recommend the best coolant for your operation. Choices are made based on the type of metal you machine and your specific operations. In general, synthetic coolants have a longer sump life than soluble oils, but synthetics have more limiting tool life properties. Semi-synthetics have very good operator acceptance, but some of the newer semis are high priced.
Comparing Coolant Types
Oil is not only a good lubricant it also helps keep our skin from drying out, especially in the winter. With this in mind, what do you think would be the best coolant to use that will keep your hands from drying out? Absolutely, a coolant that contains oil! As soluble oil coolant and semi-synthetic coolant contain oil, they are the best coolants to use when the operator’s dry hands are an issue.
Soluble oils have been used for years machining all types of metal. Soluble oils provide exceptional lubrication allowing the user to optimize finish and tool life. However, the drawback to soluble oil is that it tends to require more maintenance than other types of coolant. Extended sump life is difficult to obtain unless you have a closely-followed preventive maintenance program.
Of all the coolants in use today, semi-synthetics are by far the most widely used. The advantage to semi’s is that they are very clean to use, keeping the machine surfaces clean and providing very good sump life. As this type of coolant has evolved, improvements in additive packages now allow semi’s to approach the finish and tool life characteristics of soluble oils. In recent years we are finding semi’s that will regularly outperform soluble oil technology. The drawback to this new technology is that the “secret” ingredients (the ones that give you improved tool life and finish) are more expensive than the old standard, soluble oil.
I’ve heard people say that synthetic coolants will replace all the soluble oils and semi-synthetics because the price of oil continues to rise making synthetic coolants more popular. What you have to consider with this thinking is that many of the organic chemicals that comprise synthetic coolants are derivatives of the oil refining process anyway, and while they are not oils themselves they are dependent on oil production. Just like polymer chemicals used to make fabrics for clothing come from oil, so do polymer additives used to improve synthetic coolant performance.
Synthetic coolants typically are very clean to work with and this accounts for their popularity; however, because synthetics contain no oil they tend to be harsh on operator’s hands and exposed skin. Synthetic coolants act as a cleaner, removing the natural oils from a person’s hands, leaving no protection. The beauty of a semi-synthetic is that it too is very clean to use and in addition, the oil portion of the formula acts to protect to an operator’s skin.
Improved technology in synthetic formulations allows us to provide our customers with synthetic coolants that are capable of machining even the most difficult metals. However, cost can become an issue because these new ingredients tend to be expensive.
