I talk about coolants so much because that’s what I know more about than anything else. I guess you could say I’m in my comfort zone! Before we get into the real “meat” of what I’d like to share, let’s define some terms.
Coolant differs from cutting oils in that all coolants are added to water. Some coolants contain water as a carrier for certain ingredients and some coolants have no added water meaning that they are supplied in a highly concentrated form.
Synthetic coolants by definition contain no oil. And “no oil” means no oil of any type. Not vegetable oil or petroleum oil or “Oil of Olay.” I feel that this must be stressed when talking about synthetic coolant because in the past I’ve run across so-called synthetic coolants that contain oil. This just doesn’t make sense!
Now, at the opposite end of the coolant spectrum are soluble oil coolants. These types of products are often provided to the end user in a highly concentrated form. The drum, as received on your dock, contains mostly oil and oil soluble ingredients. When added to water, soluble oil will turn milky white. Basically what we are seeing here is an oil-based product that forms microscopic droplets of oil suspended in water. You might think of it as the milk you drink, which is essentially animal fat suspended in water.
The last type of coolant we need to consider is semi-synthetic coolant. This is very close to a combination of synthetic and soluble oil. As a matter of fact, if you had two coolants, one fully synthetic and one water soluble oil (as described above) and mixed them 50/50, you could very well come up with a coolant that closely resembles a semi-synthetic. Yes, there really is a lot more to semi-synthetics than just blending the other two types together, but I hope you see what I’m getting at.
Advantages and disadvantages: Coolant comparisons
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 an 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 have discovered 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, thus making synthetic coolants more popular. What you have to consider 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 an 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 the oil portion of the formula help protect an operator’s skin.
Improved technology in synthetic formulations allows us to provide customers with synthetic coolants capable of machining even the most difficult metals. However, cost can become an issue because these new ingredients tend to be expensive.
Changing coolant in your machine
There comes a time when even the very best coolants need to be cleaned out and recharged fresh. (This is often a good time to try something new.)
The following procedure can be used to clean out your coolant sump:
1. Remove the old coolant from the sump.
2. Remove metal fines and sludge.
3. Fill the sump with enough water to circulate through the lines of the machine.
4. Add about 1.0%-1.5% cleaner to the water in the sump. (I recommend a special cleaner which also contains a biocide to help rid the machine of bacteria.)
5. Circulate cleaner solution through the lines of your machine for an hour or two.
6. Rinse off the machine surfaces and remove the cleaner solution.
7. When you charge the machine with fresh coolant make sure that you add the coolant to the water.
8. Check the new coolant mixture with a refractometer and adjust to the proper concentration.
You now have a clean machine. Great!
Now, the best way to insure your coolant lasts a long time is to follow these simple steps:
With the procedure above, I think you’ll find your tool life will improve more than you thought possible!
This article originally appeared in Shop Talk magazine in December of 2007. Shop Talk is published
by Magellan Publishing.
