Cutting Tools

APPLYING TECHNOLOGY

by Richard J Chambers
Valcool Product Mgr
Valenite Inc, Madison Hts, MI

How to select a cutting fluid

The metalworking industry is well into the age of system solutions. What used to be the art of insert selection has been simplified and codified to the point at which it can honestly be called a technology--if not a science. Grades, coatings, and chipbreakers are all engineered to work together to perform more efficiently over a more specific range of applications and workpiece materials.

To choose a cutting fluid, consider: what you are cutting; the chemistry of your water; what you are using now; and your options.

Workpiece materials

Most shops handle a variety of workpiece materials on a regular basis. If shops cut only one material, whether it be aluminum, stainless steel, or cast iron, the selection of a good cutting fluid would be much easier to make. Unfortunately, that is seldom the case.

Photo courtesy of Valenite Inc.

For cutting aluminum or other non-ferrous metals, a non-staining cutting fluid is a must. Generally, this will be a semi-synthetic with special ingredients to prevent bi-metallic corrosion and staining of non-ferrous workpieces. For ferrous metals, however, a more general purpose semi-synthetic or hybrid fluid might be a more economical choice.

Right chemistry

The chemistry of the water is probably the single most common reason for the success or failure of a cutting fluid. Very few plants invest the money necessary to install effective water purification systems using deionization or reverse osmosis technology.

Unfortunately, the chemical present, or not present, in the water used to reconstitute a cutting fluid makes a tremendous difference in its performance and sump life. Most manufacturers of cutting fluids will perform the necessary water testing to determine exactly what minerals are dissolved in your water and make a fluid recommendation based on the results. Further, an objective analysis of the strengths and weaknesses of fluid in current use should yield a relatively small number of competitive alternatives.

Optimal options

Cutting fluids can be divided into four general groups:

Soluble oils disperse in water when emulsifiers are added. They are generally suitable for moderate to heavy-duty machining and grinding of all non-ferrous metals, carbon and cast steels, and in applications where dissimilar metals such as aluminum and steel are present. They can also be used in turning, drilling, tapping, reaming, gear cutting, broaching, as well as internal and centerless types of grinding operations. Soluble oils provide excellent aluminum and copper corrosion control, good rancidity control, and good concentrate and mix stability.

Synthetics are completely oil-free solutions made of polymers, organic and inorganic materials that are mixed with water. These clear, low foaming, and bio-stable synthetics are ideal for machining and grinding of ferrous materials, carbon steels, or cast iron. Some complex lubricant packages make them well-suited for tough-to-machine materials such as stainless steels and high-temperature alloys. Certain synthetics are specifically designed to address the primary failure modes of flank wear and nose wear. Although there are many benefits, some synthetics may cause staining of non-ferrous materials.

Semi-Synthetics fluids are a mixture of oils, synthetic emulsifiers, and water. They work extremely well on all non-ferrous metals such as titanium, aluminum, copper, brass, bronze and stainless steel in both machining and grinding. Semi-Synthetics can be used on ferrous metals, too. They are chlorine-free to reduce bi-metallic corrosion and staining of metals. They should be used at a 5% to 8% dilution with water, depending on the severity of the operation.

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