Coolants for Heavy Duty Machining

This is a copy of the post created by Monroe Fluid Technology, June 2021. Used with permission.

Written by Fred Kane, Monroe Fluid Technology

Monroe Fluid Technology has two ‘workhorse’ water soluble oil concentrates, designed specifically for the demands of heavy duty machining applications. Where a chlorinated additive is specified, our Astro- Sol C HD is recommended. In circumstances where a chlorinated additive may not be suitable, we offer Astro-Sol A-XBP. Both are low foaming products, suitable for virtually all metals and applications, and are designed to resist bio-degradation.

Astro-Sol A-XBP

Astro-Sol A-XBP is a medium-to-heavy duty biostatic soluble oil. This product was designed to be extended with water for the machining and grinding of virtually all metals except magnesium. This chlorine-free formulation is especially suited for aerospace and other applications which restrict the use of chlorine. Astro-Sol A-XBP has exceptional foam control for high-pressure operations and was designed using raw materials that have the ability to resist extreme biological degradation, thus providing a very long sump life in a properly maintained machine tool. Astro-Sol A-XBP is designed for use in metalworking applications such as all CNC milling, turning, drilling, tapping, grinding and sawing applications.

Astro-Sol C HD

Astro-Sol C HD is an extreme duty soluble oil concentrate designed for the most demanding machining operations where controlled foam and cleanliness are required. The unique combination of chlorinated extreme pressure additive, modern boundary lubricants, and a controlled-foam emulsifier package brings outstanding performance to the most severe applications. Astro-Sol C HD is formulated with a high level of stabilized chlorinated EP additive using a synthetic emulsification platform that is very stable and exceptionally low foaming. Astro-Sol C HD is designed for use in heavy-duty metal removal, deep hole drilling, tapping and threading, as well as all conventional machining and is very effective in sawing operations.

Trial Monroe Metalworking Fluids

If you have an interest in trialing one or both of these products, just inquire and we will send samples and also our Astro-Clean A, a sump cleaner you can add directly on top of your current coolant, run for 24-48 hours while making parts, then dump, rinse and recharge with the new coolant. Remember, water quality is important, so we may need a sample of your water for testing, or if you know the hardness of your water, we can resolve that issue easily.

Twin Specialties is an authorized distributor for Monroe Fluid coolants, oils, rust preventatives, and industrial cleaners. Contact Twin Specialties to learn more about Monroe Fluid’s product line and learn about our sampling and testing programs. Check out Twin Specialties’ catalog of metalworking fluids, rust preventatives, and industrial cleaners.

How to Manage your Metalworking Fluids

Metalworking fluids may not contribute that much to your manufacturing costs, but when fluids begin to fail or not work as intended, the costs could be astronomical. With the increasing costs of more technological fluids and rising disposal costs, managing your fluid and fluid consumption is more important than ever. Managing your fluids and dedicating a fluid management program could pay dividends by: reducing fluid usage, extending tool life, and improving manufacturing performance.

Monitoring Concentration

Fluid technology has advanced by leaps and bounds over the years and have improved performance for manufacturers. However, these advanced fluids have been engineered to work at specific concentrations. Running a coolant too thin or too rich will limit its ability to do its job. Running a coolant too rich might cause problems of over lubricity, but the main problem is overconsumption of the fluid.

The big problems occur when a fluid is too thin. This means the concentration in the sump is below the manufacturer’s recommendation. The additive packages are designed based on these minimum concentrations and provide enough of each additive to perform its function properly. Less concentrate means fewer biocides, fewer rust inhibitors, fewer emulsion stabilizers, etc. Eventually, the fluid breaks down quicker requiring more frequent change-outs. Some managing fluids, some operators use coolant additives/boosts to improve performance. If you vigilantly monitor concentration, the need for additives will lessen and thus reduce costs.

To monitor concentration, use a refractometer to measure concentration frequently. It is recommended to measure concentration every day or twice a day (depending on your operating schedule). The same person should measure to ensure consistency and ensure reliable measurements. When charging or recharging sumps, using automatic mixers helps ensure concentration is consistent. Remember, do not add just coolant or just water to the sump to balance out concentration. Some facilities use digital coolant monitoring systems to manage concentration, pH, and other factors. Facilities with large coolant systems may benefit from the technology.

Assessing Water Quality

Water comprises 90% or more of the fluid in the sump, thus it is crucial to make sure you are using good water. A common problem is hard water. The ions in hard water can cause chemical instability and increase the likelihood for emulsion splitting. Testing and treating your water is recommended to make sure your sump mix is working as intended. Twin Specialties can test samples of your tap water to ensure it is suitable for use in your metalworking fluid. If your tap water is excessively hard, installing a de-ionized water line is recommended for your facility. Coolant mixers can be connected directly to these lines to ensure proper mixing.

Once your water is deemed suitable, mixing the oil and water is all that is left in preparation. For the best performance and increased emulsion stability, follow the acronym O.I.L.: oil in last. This is an easy to remember acronym that will help you manually mix coolant; automatic mixers already mix using best practices.

Monitoring pH

Alkalinity is critical in the performance of your fluid. If the pH dips too low, it will no longer work and will need to be changed out. If pH drops below 8, it is imperative to raise it immediately. If pH drops below 7, the coolant is lost and must be changed. As the coolant gets more acidic (decreasing pH) you increase your risk of rusting problems. Some additives boost pH, but those may not be needed if you actively monitor your concentration. Monitoring is relatively easy, mix the fluid in the sump to get a more homogenized solution then dip a pH testing strip into the solution. Give the strip some time to change color and then match the strip to a reference sheet (usually provided with the strips). Then you can act accordingly armed with the pH information you need.

Tramp Oil Removal

Slideways and spindles require oil lubricants in order to function properly and ensure proper machining operations. These oil lubricants will leak into the sump and can cause havoc on your metalworking fluid. Some of the lubricant will be emulsified and disrupt the chemical composition of your metalworking fluid. The more oil content in the concentrate, the more likely the tramp oil will be emulsified.

This causes the growth of anaerobic bacteria. This bacterium creates hydrogen sulfide gas, which is the “rotten egg” or “Monday morning” smell that indicates coolant rancidity. The hydrogen sulfide in water also produces acids that drive down pH and alkalinity, which further damages coolant.

Synthetic coolants are excellent in rejecting tramp oils and prevent them from being emulsified. These floating oils can easily be skimmed and removed before causing damage. Using coolants below recommended concentrations limit the tramp oil rejecting additives and can accelerate this process of degradation.

Floating tramp oil can increase oil mist and smoke formation that can damage machines. The tramp oil mist also increases residues on the machine that can clog filters and destroy critical electronic components. Removing floating oil is relatively easy. Installing a skimmer, centrifuge, and/or coalescer will remove tramp oil from the sump and extend your coolants life.


Metal fines and chips may find their way into the sump. It is important that they do not remain there and are not cycled through the machine. These fines can cause wear and damage to the machine and workpiece. The fines can build up and create dead-zones when additives are trapped and do not work. The trapped additives cannot work and lead to accelerated coolant breakdown.

Filtration used to be a cost-prohibitive endeavor, but the economics of coolant management and consumption make filters a worthwhile tool. The costs of filtration have come down and filtration technology has improved, thus implementing them will reduce coolant consumption and coolant spending.

Removing Foreign Substances from the Sump

Dirt and other foreign substances can cause problems such as abrasion and pump damage. Filtering solid substances and removing them will improve coolant performance. Sump cleaners might not be fully removed and can cause excessive foaming. If that happens, using a defoamer should alleviate these issues. However, be sure to properly remove the cleaner before recharging the sump. Prevention and proper preparation are usually the best maintenance.

Managing Straight Oil/Neat Oil

Neat oils require much less maintenance than water soluble coolants. This is because neat oils do not require water, which is a breeding ground for bacteria, fungi, and mold. However, there are still a few things that you should do to maintain and extend fluid life. The main thing should be done is filtering metal fines. Removing these metal fines improve finishing and fluid performance.


Given the rising costs and improving technology of metalworking fluids, it is more important than ever to proactively manage your fluids. This can lead to extended use intervals and improved performance. Following these steps will allow your machine to get the most out of these fluids.

Twin Specialties provides a full line of metalworking fluids and additives. Additionally, our sales team will work with you to test your fluids and water to troubleshoot the problem. Contact Twin Specialties for more information about our metalworking fluids, technical expertise, and our testing and sampling program.

Should I Switch to Synthetic Coolants

For your metalworking operation, you have a variety of options in selecting a coolant to use. The first decision is selecting which classification of metalworking lubricant to use. The four main classifications are:

When selecting which fluid classification, it is important to consider: cooling, lubrication, chip removal, and corrosion protection. Each classification has its strengths and weaknesses, which should be considered when evaluating coolant needs. For certain processes, a neat oil may be better than a semi-synthetic and vice versa.

Let’s examine synthetic coolants. These contain zero mineral oil content, hence synthetic coolant. When diluted, the fluid appears transparent and is a true solution with no droplet formation. One of the main benefits of synthetic coolants is zero foaming. Foaming generally appears in fluids with higher mineral oil content. If your synthetic fluid begins to foam, it is a clear sign that the coolant is contaminated.

The chemical composition of synthetic coolants makes for a robust product and more durable solution. Synthetics are much more stable than other classifications of metalworking fluids. The robust chemistry can create solutions that can reject all tramp oils. With less tramp oils in the sump, this creates a higher performing product and less likely to become contaminated.

This allows for a longer-lasting solution and higher efficiency in recycling the fluid. To offset the higher costs of synthetic coolants, fluid consumption is reduced because the fluid is a true solution. Less concentrate is needed to recharge the solution; therefore, it will take longer to use entire container.

Metalworking fluid selection is based on finding the balance between cooling and lubrication. Synthetic lubricants are preferred in operations where cooling is important in a metalworking fluid. They are formulated for rapid heat dissipation. If your process generates a lot of heat, synthetics may be preferable to ensure temperature control and high performance.

The fluid will last longer, however that is only if you are using best practices in fluid management. Synthetics are designed for specific concentrations and are less forgiving than other classifications of metalworking fluids. Tighter concentration control is needed for synthetics and you have to monitor the solution daily. Even though fluid management is more rigorous, it is easier to control and measure concentration because it is a transparent and droplet-free solution.

Whether you are facing foaming problems, high temperature operations or shorter coolant lifespans, the decision to switch to a synthetic coolant may be one to consider. Even though synthetic coolants are generally more expensive than other coolant classifications, the benefits will reveal themselves as you use the synthetic coolant. A synthetic coolant will last longer than a soluble oil and is much easier to reclaim and recycle. The performance of synthetic coolants is superior than semi-synthetics and will cool the work-piece and tool more effectively. Superior chemical formulation will protect your sump from tramp oils and other outside contamination. This protection along with zero-foam will keep your operation running longer with reduced downtime. Your coolant concentrate will last longer and can create significant cost savings over time.

How to Test Fluid Samples

You have pondered switching your metalworking fluid. Whether it is a soluble oil, straight oil or synthetic, it is crucial to give your sample a fair test. Many times a superior product may test worse than its inferior equivalent due to a poor testing environment. There are many factors to consider when setting up the testing environment, as well as how you are going to test the sample.

Prepare the Testing Environment

Once you have established a time to test new fluids, it is important to include time to prepare the environment. In scientific experiments, scientists meticulously craft the environment to get controlled and accurate results, the same should apply to your fluid test. Depending on your process, preparation may involve: draining the sump, wiping down parts, running a cleaner through the machine, or changing your tools. It is important to have a fresh and consistent environment as you will reduce the amount of variables that may affect performance.

Determine Testing Metrics

Firstly, you and your team should determine what is going to be monitored. It is best to use a typical process for a given machine. The results will give better insight if you are machining a component that you regularly make. If you are testing a heavy-duty product, using a complex process will allow you to observe the sample in tougher conditions. You can test for a variety of quantitative and/or qualitative factors such as: foaming, evaporation rate, performance and residual film. Whatever you want to monitor and improve, setting clear goals will aid your analysis.

Run a Baseline Test

Secondly, run a test on the current fluid. Ensure that the fluid is fresh and the machine is in proper working order. On occasion, a fluid may perform poorly because it has not been maintained properly or incorrectly used. Consult technical data sheets to determine best practices for the fluid. Sometimes, your issue be resolved if proper usage and maintenance are practiced. Measure your results and then reset the testing environment for the sample(s).

Sample Testing and Decision-Making

Finally, test your sample(s) with the exact same process as your baseline test for an accurate comparison. It is important to prepare the testing environment to the conditions best suited for the sample. Consult technical data sheets for determining proper concentration and operating conditions. These conditions may differ from the baseline test and differ among different samples. Once complete, you can compare the results of the sample test and the baseline test and determine which product is the best.

Once the testing is complete, you and your team should compare the results of the sample(s) against the baseline and make a decision on which fluid to use going forward. It is important to consider other business and economic factors as well. Things like price, lead time and availability are also important as these could impact the bottom line and productivity.

Post-Decision Considerations

After a final decision has been made, it is important to set up a proper operating environment going forward. Set up new operating procedures to produce a consistent operating environment and communicate the changes with your team and machine operators. This ensures maximum performance of the fluid and reduces the likelihood of having to switch and go through the testing process again. If a switch is made, you must figure what to do with the remaining fluid left at your facility; some options include: using up the remaining fluid, reselling or returning the fluid, or disposing of the fluid with an environment services company.

Best Practices for Lubricant Storage

Lubricants are a critical component to any machine, engine, or tool. How you manage and store the lubricants is as important, if not more so than the actual lubricant selection. In controlled situations, higher quality lubricants will consistently outperform their inferior counterparts. This difference is clearly seen in comparisons of oil-based lubricants (Group I-III) and synthetic lubricants (Group IV – V). However, controlled tests are not going be perfectly replicated in the work environment. Proper storage and monitoring can be the difference between high performance and early breakdowns.

The shelf life for lubricants depends on a variety of factors such as: base oil, additives and thickeners. It is often best to consult the manufacturer to determine the shelf life for your lubricants. Regardless of the lubricant’s shelf life, it will never be actualized if it is not stored properly. This leads to many problems on the manufacturing floor that have a major impact on the bottom line. This can lead to increased costs, machine breakdowns and lower-than-expected productivity.

Consistency is Key

What is the key characteristic for storage best practices? Consistency. By having consistent and routine storage practices, you will have the confidence that your lubricants will perform up to manufacturer’s stated standards. A consistent and controlled environment can also help you diagnose and remedy issues that may arise in your lubricant. For example, if your oil analysis shows that there are higher levels of moisture, you can more effectively diagnose the root cause of moisture. In poor conditions, there are many factors that can affect moisture found in oil-based lubricants, but controlled environments eliminate many of these root causes or isolate them to one-off instances (e.g. a loose oil cap, a small leak or the occasional spill).

Creating the Ideal Environment

The best way to ensure an optimal environment is to dedicate a room solely for lubricant storage. The room should be climate controlled thus protecting lubricants from the heat or the cold. As temperatures reach extremes on either end, the lubricant can breakdown and fall short on performance and shelf life. This is especially important with greases where low temperatures can affect additives. Indoor storage also protects lubricants from airborne moisture. Moisture in lubricants reduces reliability and performance and will lead to more machine breakdowns and downtime.

The storage room should be further away from any external entrance such as a shipping and receiving area or an employee exit. Lubricants near these areas are at risk to exposure outdoor weather and particle contamination. Particles in the lubricants must be filtered out or else machinery will experience greater wear and a reduce life expectancy. By storing lubricants away from shipping and receiving areas, this allows facilities to have less congested work areas and allow for efficient movement or parts, supplies, products and people.

What is the ideal environment for storing lubricants? We recommend a cool, dry area that protects the products from moisture and extreme temperatures. This means storing them in a room or floor area that is away from any external windows or doors, in a well ventilated area, and clearly separated from any workstation.

Improving Storage for End-Users

The lubricant storage room should efficiently use space, but also have the capability to expand. It is important to have all lubricants to be easily accessible so you can properly fill up the right amount of lubricant without spilling and potentially contaminating other lubricants. Many machine breakdowns occur when two incompatible lubricants are mixed. This error is preventable and the best way to ensure proper collection is to have clear and visible labels on each container. This includes having manufacturers labels clearly displayed, having color-coded labels to indicate product type, end-use or receiving date.

Another good idea is to organize containers based who uses them at their workstation. If one person uses the majority of a certain lubricant, it is sensible to store that product close to other products he or she may use. This creates an efficient process for people to collect their lubricants and reduces potential confusion and human error.

One of the greatest root causes of lubricant mismanagement and machine breakdown is human error. It happens to all of us. We are not perfect, but it is critical to strive to improve and implements rules and procedures to minimize these errors. Having properly tuned equipment ensures lubricants are properly measured out each time. Another good measure is to limit who has access to the lubricant room and ensure it is locked when not in use. When access is well controlled this reduces spillage, waste and in some cases, theft.


Theses some of the basic measures that can be taken to ensure a stable and consistent environment. We cannot control the weather, but we do have authority on the thermostat. Storing the lubricants in cool, dry area will ensure maximum shelf life. The additive packages will work properly and the performance you seek from a lubricant, will be realized and performance will improve.

Accidents happen and we learn from our mistakes. The most important thing to learn is preventing similar accidents in the future. This may involve changing processes, reworking access, or using different equipment. Making these changes ensure that mistakes are limited. It is important to regularly assess these processes ensure your lubricants are up to specifications and waste or damage is reduced. By following these best practices, your facility will be cleaner, organized and more efficient.