Image of Understanding The Mechanics of Metalworking Fluids

Understanding The Mechanics of Metalworking Fluids

We usually don’t think of metalworking fluids for coolant maintenance as mechanical, but this is the most important aspect. Ultimately, it keeps the chemistry and biology in proper order. There is a direct link between what we do (or don’t do) at the mechanical level to what goes on at the microscopic level.

By mechanics we are specifically referring to keeping the fluids moving and removing foreign contaminants. These contaminants include tramp oils, emulsified oils, particulates created from the machining process, and any other thing that may end up in the sump.

Metalworking Fluid Research

Remove the Oil Layer

This layer is what seals off the air supply to the sump and provides nutrients for the bacteria. By keeping oxygen from the coolant, anaerobic bacteria will thrive. These types of bacteria are more dangerous to the chemical components of the coolant than any other types. The oil acts as their food source and they combine with it to create a biofilm, which forms somewhat of a skin on the surface. These biofilms are difficult to remove, and once the particulates are formed, the exposure will only lead to contamination of the entire machine.

The simplest method to reduce and remove floating oils are a variety of mechanical skimmers, which mount to the sump. They pull off the oil layer with some type of media (disk, belt, or tube), and drain it to a collection container. Some of this variety are also equipped with a mini separation tank so there is no wasted coolant, as it may be picked up during the process. This is because most coolant contains some type of mineral oil.

There are also coalescers, which pull the oil off via a collection apparatus, and transfer it to a drum or tank for separation. The de-oiled coolant then is introduced back the sump. This type of unit is the best type for the health of your fluids, since it requires very little maintenance and keeps the fluid in circulation. Some of this variety also incorporate additional aeration devices and can filter small floating particulates.


Metalworking Fluids working

Keep the Metalworking Fluids Moving

Circulation of the sump is as important as any other mechanical method practice. It keeps samples moving, forcing oxygen into the system. Oils have a harder time pooling on the surface, which helps to prevent contaminated bacterial biofilms. If you have any doubt about this strategy, think about how an aquarium works, and why materials in ponds can go stagnant.

It may not be feasible to leave the coolant pump on at all times, so instead, a small centrifugal pump can be introduced to the sump to keep the coolant from remaining in a static state. If the machine sump is divided, all baffles should be agitated. Small aerators can also perform this function if the sump holds 50 gallons or less.

Keep in mind any coolant that pools in the lines is affected by the same forces in play. When machine sumps are emptied, cleaned, and recharged, these lines are usually overlooked. Bacterial contamination still exists within the system.


metalworking fluids at work

Remove Particulates

Finally, both floating and sinking chips should be removed from your metalworking fluids. This way they do not interact with the chemical components of the fluid to cause premature failure. Although most of the material sinks the bottom, even if a conveyor is in operation, they will interact with any fluids that they touch. A shovel or industrial vacuum may be used to remove the larger, sinking chips.

A general filtration system should be used regularly to remove all others. Some floating chips may be filtered via a coalescing unit with this capability. However, very fine chips, such as 5-25µ in size, should be removed after the oil has separated, or re-emulsion can occur.


metalworking fluids CNC machine


Metalworking Fluids Case Study:

Saving money and preventing machine downtime

As plant supervisor of Case Grinding in Garfield Heights. Ohio, Rick knows the vital role that skimmers play in maintaining coolant and other metalworking fluids. This is why his management team fills his shop with Zebra Sidewinder™ Tube Skimmers.

Saving money and preventing equipment downtime were the most important factors in their decision to install the skimmers. From the automotive industry to aerospace, their customers rely on them to manufacture motion control linear positioners and tension transducers.

Case Grinding machines everything metal from aluminum, brass, to stainless steel and some exotics in their programs. And their CNC’s often operate for 12 or more hours at a time. These conditions wreak havoc on even the best coolants.

Finding a solution to his coolant’s tramp oil problem had to be both efficient and cost-effective.

He wanted a skimmer that would run continuously. It needs to be easy to install. Finally, if a potential problem came up, help would be just a personal phone call away. Zebra Skimmers in local Solon, Ohio got the call.

Rick decided to use the newest type of skimmer, the Zebra Sidewinder. He got them first for his Hitachis and Hurcos. Before Zebra, he had to change his coolant sumps every 3-4 months which was a hazard.

Since using the standard Sidewinders over the past 2 years, Rick has seen his coolant sumps last much longer. On average, they now last over a year before they need to be changed. And in several cases, the sumps have gone almost a full 2 years without the need to be cleaned out. Equally important, his co-workers are not complaining about foul odors and skin problems anymore.



Rick had a vertical Hurco that was generating a lot of oil, and a lot of fines. In response, Zebra developed its newest member of the Sidewinder family, the Sidewinder V. Rick required such improvements as the external scraper to prevent fines from clogging the drain, a 1″ inner-diameter discharge port for easy cleaning and reduced maintenance. Most significantly, it had a total oil capacity flow over 1 quart per hour.

Like earlier Sidewinders, this tool has a specific continuous-duty motor, and would still fit in even the most access-impaired machines. This, coupled with its increased capacity, meant that Rick could use the unit on several machines without having to worry about how the skimmer would bring out the oil. In addition, the Zebra Sidewinder features a transparent cover that enables him to see the skimmer in action.

Finally, the torque of his new Zebra Sidewinder allows Rick to use an O-ring of almost any length for his processes. Unlike most skimmers, the O-ring allows the skimmer to move from a deep machine to a shallow machine sump with no work involved. Since the unit can’t bottom out like a disk or belt skimmer, it gave Rick’s operations even more flexibility as to where it can be placed. And because it can be mounted with a single C-clamp, his team has the convenience of moving it around the workplace in a matter of minutes.


Once an employee safely installed the skimmer on his metalworking fluids, he was amazed at the speed at which tramp oil was removed. He was also pleased to learn that very little coolant is removed from the sump despite the faster speed. Rick also noticed an improvement in the quality of his expensive coolant. He especially liked the fact that they were able to install the skimmers to his systems without having to shut the machines down, as you have to do with many other types of skimmers.

Rick takes a pro-active approach to coolant maintenance. By using a refractometer in conjunction with a mixer, he gets the right concentration of coolant for each machine. In this way he gets peak performance out of his fresh coolant, but doesn’t waste coolant either. This saves lots of money in the long run.

Zebra’s customers also enjoy refractometers which are water-tight, pre-focused, and unbreakable. Zebra’s economical mixers feature precise needle-valve control, providing consistent mixing every time. Finally, the protection of an oxygenator, a device that injects oxygen into coolant sumps helps with the overall individual effects of these machines. In this way the volume of aerobic (good) bacteria is enhanced, while the growth of anaerobic (bad) bacteria is suppressed.

Save more time cutting your metalworking fluid costs and enhancing your program with Zebra Skimmers. Contact us today and let us help you and your employees with tramp oil removal.



About Zebra Skimmers:

Our mission has always been simple. It is to provide the metal working industry with the oil skimmers and metalworking fluid management systems they need to complete jobs quickly and efficiently. Innovative and affordable solutions have gained us many accolades. Our continued growth is due in no small part to our excellent customer service… Not to mention our satisfaction guarantees and the performance of our tools.

Among our diverse options of oil skimmers and metal working fluid management systems, you can expect to find: