A proper evaluation protects the bottom line
November 2019 - There are four primary types of coolants: straight oils, oil soluble, semi-synthetics and synthetics. The Steco Corp. has decades of experience making oil-based cutting fluids and has worked to engineer and test a viable water-based metalworking fluid.
Recent innovations in chemical ingredients enabled the development of Tap Magic H2OX, a water-soluble metalworking fluid, and provided insight to the ways coolants can be maximized, depending on the application.
The main difference among the coolant types is the oil content in the concentrates. The base oil content is approximately defined as:
• Straight oils, 100 percent base oil and additives
• Oil soluble, 30 percent to 85 percent base oil
• Semi-synthetics, 5 percent to 30 percent base oil
• Synthetics, 0 percent base oil
Each type has strengths and weaknesses for machining and cutting. Straight oils have great performance but cannot properly cool the work surface and often are hard to pump through recirculating systems. Oil soluble coolants have good performance but don’t cool well and may leave a sticky residue on parts and equipment. Synthetics have excellent cooling ability; however, it is tougher for them to protect tooling due to a lack of lubricity. Semi-synthetics bridge the gap by providing cooling ability with performance and have been steadily gaining market share in recent years.
Coolant variables
Users need to consider several factors before choosing a coolant. A suitable solution for one shop may not be optimal in another. First, determine the type of coolant needed. (See Figure 1 for the typical information needed to make this decision.)
Next, review skin sensitivity, water condition (hard or soft), the types of metal being machined, machining application (honing, milling, broaching, sawing, etc.), disposal regulations, surface finish requirements, tool life, sump life and corrosion.
Fluid application methods include flooding, misting, minimum quantity lubrication (MQL) and high-pressure systems. Each of these has advantages and must be matched to the type of work performed. Based on the list above, the choice of coolant can require a customized solution to fit a specific set of circumstances. Semi-synthetic fluids are the best type to research if a single fluid for all operations is desired. But there is more work to do to truly optimize the use of coolants.
Dilution optimization
Total cost reduction for coolant use is an obvious goal in any shop, but dilution percentage of the concentrate can’t be viewed as simply a minimization exercise. During our testing in one process, we saw moderate results with a typical 5 percent dilution on grade 316 stainless, while a 9 percent dilution proved to have excellent results in extending tool life. While the cost of the coolant increased slightly due to the higher concentration, the improved tooling cost savings provided for a significant net decrease in total cost.
Some shops try to maintain a standard dilution through a variety of jobs and operations. This approach simplifies ordering and inventory management of lubricants, but more and more shops are now developing sophisticated dilution parameters that work best for various applications and metals.
Net-cost decisions
When searching for a fluid solution, some shops or plants may find a suitable one-size-fits-all coolant that can be used across their operation, while others may find it worth the effort to invest in a fluid management system where each process uses a different dilution or even different fluids.
Coolant net costs include coolant cost (including coolant price, dilution, fluid longevity and coolant maintenance); tooling cost; recycling/disposal programs; fluid application; and lubricant inventory.
Analyzing net cost and exceeding customer requirements provides an advantage over simply looking for the lowest purchase price. Although an inexpensive fluid can be appropriate, it also can be costly in the long run if a high-quality coolant would provide more value to your operation. A lot of time and effort is spent choosing the right equipment and tooling, and using that same approach for your fluids will yield big results.
Ken Gaines is president and CEO of The Steco Corp., which makes Tap Magic industrial lubricants. The company has worked for over 60 years to continuously improve its products to benefit the metalworking industry.
