Metalworking Fluid Definitions

Here is a short list of definitions of metalworking and metalforming terms to help you better understand how to get the best performance from our fluid products.

Antioxidants are frequently added to industrial products. A common use is as lubricants to prevent oxidation, and to prevent the polymerization that leads to the formation o fouling residues. Antioxidant polymer stabilizers are widely used to prevent the degradation of polymers such as rubbers, plastics and adhesives that causes a loss of strength and flexibility in these materials.
Base â€‹is the name given to lubrication grade oils initially produced from refining crude oil (mineral base oil)
A chemical agent used to kill microbiological organisms (bacteria or fungus) in metal working fluids.
Boundary Layer
The layer of fluid in the immediate vicinity of a bounding surface where the effects of viscosity are significant.
Boundary lubrication
Lubrication by a liquid under conditions where the solid surfaces are so close together that appreciable contact between opposing asperities is possible.
These additives are in the form of a chloroparaffin or chlorinated olefin. This is present as an extreme pressure (EP) lubricant in some metalworking fluids which are designed for use on ferrous metals. It is believed that chlorinated olefins break down chemically under the influence of (extreme) heat and pressure near the cutting or grinding zone, to form a solid lubricant film between the ferrous work piece and the tool. Although the same break down mechanism and film forming is unlikely in the case of aluminum, it has been observed that chlorinated olefins can help in the cutting or grinding of aluminum alloys, especially automotive alloys.  However, since there are other (non-chlorinated) lubricants that work just as well with aluminum it is generally best to avoid chlorinated olefins when cutting or grinding aluminum. 
Substances contained in the metalworking fluids that are not part of the original make-up. These can be abrasive particles, tramp oils, metal particles, dissolved metals, dirt, hard water salts, bacteria, fungi and microbiological byproduct.
Corrosion Inhibitor
A corrosion inhibitor is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy.  The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime.
DI Water
Deionized Water also called "DI Water" or "Demineralized Water", simply means the removal of ions. Ions are electrically charged atoms or molecules found in water that have either a net negative or positive charge. For many applications that use water as a rinse or ingredient, these ions are considered impurities and must be removed from the water. Ions with a positive charge are called "Cations" and ions with a negative charge are called "Anions". Ion exchange resins are used to exchange non desirable cations and anions with hydrogen and hydroxyl, respectively, forming pure water (H20), which is not an ion.
Distilled Water
Distilled Water removes more impurities than just ions. This process removes nearly all minerals, many chemicals, and most bacteria. That doesn't mean that it removes everything, however, especially if the water contains volatile organics and certain other contaminants. These impurities will evaporate and stay in the distilled water. As with deionized water, pre-treatment filtering is an important step.
A mixture of liquids that do not dissolve into each other to form a true solution. This is generally an oil and water mix. 
An emulsifier is a substance added to metalworking fluids to aid in forming an emulsion in the fluid.
Ester Based
​Ester oil is synthetic base oil that has been chemically synthesized. Esters are stable molecules, provide good solvency, and provide very good low-temperature and high-temperature performance. Esters as have a fair hydrolytic stability, good biodegradability, very good lubricity, and excellent oxidative stability. Modern synthetic esters can be tuned to perform in nearly any environment and application. Whether you seek excellent hydrolytic stability, oxidative stability, biodegradability, lubricity, high viscosity index or low-temperature properties, all of these are possible with the right synthetic ester.
Extreme Pressure Agents
​Extreme pressure additives, or EP additives, are additives for lubricants with a role to decrease wear of the parts of the gears exposed to very high pressures. They are also added to cutting fluids for machining of metals. Extreme pressure additives typically contain organic sulfur, phosphorus or chlorine compounds, including sulfur-phosphorus and sulfur-phosphorus-boron compounds, which chemically react with the metal surface under high pressure conditions. Under such conditions, small irregularities on the sliding surfaces cause localized flashes of high temperature (300-1000 Â°C), without significant increase of the average surface temperature. The chemical reaction between the additives and the surface is confined to this area.
Heat Transfer
Heat transfer fluid is one technical term used in high temperature as well as low temperature manufacturing applications. 
​The lubricity of a substance is not a material property, and cannot be measured directly. Tests are performed to quantify a lubricant's performance for a specific system. This is often done by determining how much wear is caused to a surface by a given wear-inducing object in a given amount of time. Other factors such as surface size, temperature, and pressure are also specified. For two fluids with the same viscosity, the one that results in a smaller wear scar is considered to have higher lubricity. For this reason lubricity is also termed a substance's anti-wear property.
Neat Oil
Product as it comes from the container, not diluted. 
Metalcutting Fluids
Products that offer extreme pressure additives and form a boundary layer in the CNC Milling, Turning and Sawing process
Metal Removal Fluids
Fluid products used in Cutting, Grinding, Milling, Drilling, Honing, Tapping, Reaming operations.  
Also see above "Metalcutting Fluids"
Metalworking Fluids
Any of the group of coolants, fluids, rust inhibitors, etc. that are use in the Industrial manufacturing sector in the metalcutting or metalforming process.
Nonpolar Oils (ingredients)
Nonpolar Oils are hydrocarbons. They lack an electron­egative element like oxygen, which results in their typical hydrocarbon feel.
Polar oils (ingredients)
Polar Oils contain heteroatoms that differ in electron­egativity. This results in a dipole moment. Typical polar oils are fatty alcohols, esters and triglyce­rides. While they are still water insoluble and oil-loving, these oils have unique characte­ristics due to their polar nature. They require higher HLB emulsifiers to make stable emulsions, they dissolve materials that are insoluble in nonpolar oils, and they provide unique properties when compared with nonpolar oils such as mineral oil.
​A refractor measures the amount of solids (concentricity) in a given product. In the metalcutting industry refractometers commonly use a Brix Scale.  To measure the concentration you may need to use a refractometer multiplier.  See Below
Refractometer Multiplier
The lower the number the more solids there are, the higher the number the more watered down the product is.  Solid Oils are generally 1:1 while other coolants such as semi synthetics have different multipliers.  The value on your refractoromter needs to use the multiplier to get the correct concentricity range.  For more information please read: How to use a Refractometer for Measuring Metalworking Coolant Concentricity.
Selective Depletion - The additive package or ingredients gets depleted over time from machining processes or can in some cases be carried out with swarf/chips.  
​Semi-synthetic coolants can contain anywhere from 5% oil to 35% oil. The smaller percentage of oil in semi-synthetics allows for heat to be dissipated much faster than with soluble oils, offers good rust control and longer sump life. Much like soluble oils, chlorine is sometimes added to improve heavy machining performance. Nanotech coolants are especially popular in applications that require added tool life and cleanliness.
Straight Cutting Oil
Straight Oils, also referred to as neat oils, are petroleum or vegetable based oils that do not contain water. They are used as is or “straight” without being diluted. Straight oils are used in metalworking applications where lubricity is more critical than heat reduction. Straight Cutting Oils are used for applications where water soluble coolant is unsuitable. With higher boiling points than water, oils can be raised to considerably higher temperatures (above 100 degrees Celsius) without introducing high pressures within the machine's sump. Cutting oils provide heat transfer, lubrication, pressure transfer (hydraulic fluids), and perform several such functions at once.
Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids, between a gas and a liquid, or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents, and dispersants.
​Synthetic Cutting Oils do not contain a mineral oil base or petroleum. Instead, they're formulated from the alkaline organic and inorganic compounds alongside additives to prevent corrosion. They function well in their diluted form.
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is highly interdisciplinary. It draws on many academic fields, including physics, chemistry, materials science, mathematics, biology and engineering. People who work in the field of tribology are referred to as tribologists.
Tramp Oil
This is a petroleum contaminant of a metalworking fluid. Usually hydraulic oil, gear oil, way oil, and other lubricants.  
Water Soluble Oils
​Water Soluble Oil, also called Water miscible oil or water mixable oil, is oil based coolant either engineered or an emulsifier has been added, to be thinned and cleaned up with water.
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