Glossary of Metalworking Fluid Terms

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ACGIH - American Conference of Governmental Industrial Hygienists. ACGIH is one of the sources cited on the OSHA MSDS.

Acid - A substance that releases protons (H) in water. Acids lower the pH of aqueous solutions.

Acid Number - A measure of the acidity of a substance based on the milligrams of potassium hydroxide required to neutralize the free fatty acids in one gram of the substance. It is often used with oil, fat, wax, and resin.

Acute Health Effects - Health Effects that occur rapidly as a result of a short-term, one-time exposure.

Alkalinity - The concentration of basic or alkaline components in a mixture, determined by titration with an acid.

Amide - Organic amides are formed by a condensation reaction of a fatty acid and an amine. Amides are used as emulsifiers and corrosion inhibitors in various materials, i.e. metalworking fluids, shampoos, soaps, etc.

Amine - A nitrogen containing organic compound having the general formula NR₃ where R may be either a hydrocarbon or hydrogen.

Anionic Surfactant - A surface-active agent that when dissolved in water carries a slight negative charge. They are used in various materials, i.e. metalworking fluids, shampoos, soaps, etc., as lubricants, emulsifiers, corrosion inhibitors. Anionic surfactants are more sensitive to water hardness than nonionic surfactants.

Aqueous - Refers to water, such as water-diluted metalworking fluid mixes are aqueous.

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Bacteria - Single-celled, microscopic organisms that are widespread in our environment. They are found in a variety of shapes (round, rod, or spiral). Most bacteria grow well on organic substances, although some survive on inorganic material.

Bacteria, Aerobic - Bacteria that requires oxygen to grow and replicate.

Bacteria, Facultative Anaerobic - Bacteria that can grow in either the presence or absence of oxygen.

Bacteria, Obligate Anaerobic - Bacteria that need an oxygen-free environment in order to survive.

Bacteria Count - A measure of the amount of bacteria in a mix. Bacteria Counts are determined for metalworking mixes by dip slides, total plate counts, and other measures. Bacteria Counts for metalworking fluid mixes are usually expressed as 10^x bacteria per milliliter.

Base - A substance that releases OH- ion. Basic materials incease the pH of aqueous solutions.

Biochemical Oxygen Demand (BOD) - A measure of the amount of oxygen used by microorganisms during the process of decomposing organic compounds. The BOD is usually measured in milligrams per liter or in parts per million of oxygen required. Because most metalworking fluids contain biocides, BOD determinations are not usually performed on them.

Biocide - A chemical added to a metalworking fluid product or mix designed to eliminate the growth of microorganisms. This broad term includes bactericides, fungicides, and microbicides.

Biodegradable - Capable of being decomposed by microorganisms.

Blue M - A humidity cabinet in which the temperature and Relative Humidity can be held within close parameters. Often used in the evaluation of the corrosion protection provided by a product.

Boundary Lubrication - A thin layer of lubricant that physically adheres to the surface by molecular attraction of the lubricant to the metal surface. Examples are fats, fatty acids, esters, and soaps.

Built-up Edge (BUE) - The pressure welding of the workpiece to the cutting edge of the tool.

Burn - A change in the material caused by the heat of the metalworking operation. Burns are often indicated by localized discoloration.

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Carcinogen - Capable of causing cancer or malignant tumor formation.

CAS Number - Chemical Abstract Services Registry Number. A number that identifies a chemical. It is assigned by the Chemical Abstract Services.

Cationic Surfactant - A surface-active agent that when dissolved in water carries a positive charge. Cationic surfactants are used in metalworking fluids, shampoo conditioners, and other items as preservatives, fungicides, etc.

Centipoise - Unit of viscosity measurement (0.01g/cm-second).

Centrifuge - A device that uses a spinning bowl and the differences in specific gravities of materials to separate one from another. Centrifuges can be used to separate loosely emulsified and free oils from water-diluted, metalworking fluid mixes.

CERCLA - Comprehensive Environmental Response Compensation and Liability Act, administered by the EPA (U.S.).

CFR - Code of Federal Regulations, US

Chelating Agent - A molecule capable of attaching itself to a metal ion by two or more linkages to the same molecule. A common example is Ethylene Diamine Tetraacetic Acid (EDTA) that are used in water-diluteable metalworking fluids to address chelate Ca and Mg in the water.

Chemical Oxygen Demand (COD) - The amount of oxygen required for total chemical oxidation of matter in water.

Chloride - A salt resulting from the neutralization of HCI, i.e. sodium chloride (NaCI). High levels of chlorides are corrosive.

Chronic Health Effects - Adverse health effects resulting from long-term exposure, or persistent health effects.

Coagulation - The clumping together of solids to make them settle faster. Coagulation can occur with the use of certain chemicals that are often referred to as settling or filtering agents.

Coalescence - The growing together or uniting process that occurs between similar materials, such as when oil droplets agglomerate on a plastic media.

COC - Cleveland Open Cup. This is one of the standard devices used to measure flash and fire points.

Concentration - A measurement of the content of one or more materials in a metalworking fluid. There are various methods for determining the concentrations of the different materials in metalworking fluid mixes, such as the NS Titration for anionic materials and the Total Alkalinity for alkaline materials.

Conductivity - A measurement of the ability of a metalworking fluid mix to conduct an electric current. It is dependent on the amount of dissolved ionic material. High levels of conductivity (i.e. 4.0 MilliSiemens/cm) can promote problems with the metalworking fluid, such as insoluble residues, mix instability, and loss of overall performance.

Corrosion - Corrosion is the partial or complete wearing away, dissolving, or softening of any substance by chemical action. Rusting, staining, pitting, and etching are forms of corrosion.

Coupling Agent - A chemical additive that aids in emulsion formation by being mutually soluble in both phases.

Cutting Fluid - A fluid that is applied to a tool to promote a more efficient machining operation.

Cutting Speed - Tangential velocity on the surface of the tool or workpiece at the cutting interface.

Cyclone Filter - A device that separates a mixture according to density by means of centrifugal force. Cyclones are used for cleaning metalworking fluids (separating dirt particles, chips, etc.) and have no internal moving parts.

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Defoamer - Chemical additive that physically alters the surface tension of a fluid to reduce or eliminate foaming.

Density - The mass of a material divided by its volume.

Dermatitis - Inflammation of the skin that is evidenced by a rash, itching, blisters, or crustiness.

Dirt - Metal chips, fines, swarf, grinding grit, etc. found in a used metalworking fluid mix.

Dirt Volume - The percentage of solids in the metalworking fluid mix that is separated from the mix by settling or centrifuging. High dirt volumes usually indicate either inadequate filtration or filter problems. A high dirt volume can affect the performance of the metalworking fluid and lead to such problems as residue, poor finish, poor tool life, and microbial growth.

Dissolved Oxygen (DO) - Oxygen that is dissolved in water. Microbial activity will cause the DO to drop.

DOT - Department of Transportation, U.S.

Dry Film Lubrication - A lubricating film consisting of a dry carrier medium with suitable lubricity pigments, such as molybdenum disulfide (MoS2), PTFE (Teflon®), and graphite, that provides a tough, durable, solid film lubricant.

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Effluent - Waste water leaving a waste treatment process, relatively cleaner than before.

Emulsifier - Substances that prevent dispersed droplets coming together in emulsions by reducing interfacial tension. Emulsifiers have both oil-soluble and water-soluble portions in the same molecule.

Emulsion - A disperse system consisting of several phases which arises through the mixing of two liquids that are not soluble in each other.

Entrained Air - Air that is in suspension and is slow to rise to the surface.

EPA - Environmental Protection Agency, U. S.

EPCRA - Emergency Planning and Community Right-to Know Act (a.k.a. SARA). EPCRA is one of the reference sources used when developing an OSHA MSDS.

Epidermis - Outer layer of skin.

Extraneous Oil - Often called "tramp oil," is the oil or oil-like material in a fluid that is not from the metalworking fluid concentrate.

Extreme Pressure (EP) Lubricant - A compound (usually containing chlorine, sulfur, or phosphorus) which reacts with the surface of the metal or tool to form compounds (chlorides, sulfides, or phosphates) which have lower shear strength than the base metal. These compounds can help provide longer tool and grinding wheel life in the moderate to heavy-duty operations.

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Fat - An animal- or vegetable-derived additive comprised of glycerol esters of fatty acids. Examples are lard oil, tallow, castor oil.

Fatty Acids - A family of organic acids, so-called because these chemicals are derived from animal or vegetable fats. Fatty acids are used in many products, i.e. metalworking fluids, soaps, cosmetics, etc, as emulsifiers, lubricants, mildness agents, etc.

Ferrous - Refers to iron. Steel, cast iron, and other iron-based alloys are called "ferrous metals."

FIFRA - Federal Insecticide, Fungicide, and Rodenticide Act (U.S.).

Filter Media - Any porous material (usually paper, cloth, or screen) that traps solids when a cutting fluid passes through.

Finish - Surface quality or appearance.

Fire point - The temperature at which a sustained flame will burn for at least 5 seconds, usually slightly higher than the flash point.

Flash Point - The temperature at which a brief ignition of vapors is first detected.

Foam - Air dispersed in a liquid causing an increase in the volume of the liquid. Foam is usually seen as bubbles on the surface of the liquid that may break quickly or be quite stable.

FOG - In waste treatment, the content of Fat, Oil, and Grease.

Free Oil - The amount of oil or oil-like material in a metalworking fluid mix that easily separates and floats on the top of the metalworking fluid mix.

Fungi - Aerobic microorganisms consisting of either single-celled yeast or filamentous mold.

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Galvanic Corrosion - A common type of corrosion process in which a potential difference through an electrolyte causes surface attack at the interface of two dissimilar metals.

Gram (g) - Metric unit of mass. There are 453.59 grams in a pound (avoir du pois: U.S. or British); there are 1000 g in 1 kilogram (kg).

G-Ratio - A measure of grinding performance defined as the volume of metal removed divided by the volume of grinding wheel worn away in the process.

Grinding Fluid - A fluid that is applied to a grinding wheel to promote a more efficient grinding operation.

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Hardness (water) - The combined calcium and magnesium content of water. Water hardness is usually expressed as parts per million (ppm) of calcium carbonate (CaCO₃). Water hardness can adversely affect the metalworking fluid mix, leading to insoluble residues, mix instability, corrosion, and loss of overall product performance. Each ppm of calcium contributes 2.5 ppm of hardness and each ppm of magnesium contributes 4.1 ppm of hardness.

HMIS - Hazardous Materials ldentification System (U.S.).

Hydrodynamic Lubrication - Exists when a coherent lubricating film of liquid separates the surfaces sliding over each other.

Hydroforming - A method of shaping metal by forcing it over a flexible die filled with fluid.

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IARC - International Agency for Research on Cancer. IARC is one of the reference sources used when developing an OSHA MSDS.

ISO - Abbreviation for International Standards Organization, located in Geneva, Switzerland.

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Kinematic Viscosity - A function of both internal friction (viscosity) and density of the fluid.

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LD₅₀ - Acute or single dose of a substance producing death in 50% of the test animals within 14 days of exposure.

Lubricant - A substance capable of reducing friction, heat, and wear.

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Metalworking Fluid - A liquid used to cool and/or lubricate the metalworking process.

Microbicides - Substances used to prevent and address microbial growth in water-diluted, metalworking fluid mixes.

Micron - A measure of length, one-millionth of a meter.

Microorganisms - Minute living organisms, including bacteria, yeast, and molds.

Milliliter (ml) - Metric unit of liquid measure. There are 946.3 ml in 1 quart (U.S.); there are 1000 ml in 1 liter (1).

Mineral Oil - An oil of mineral origin; especially : a refined petroleum oil.

Mold - Filamentous microorganisms composed of many cells; may grow in metalworking fluids, interfere with filtration, and clog pipelines.

MSDS - Material Safety Data Sheet. A form containing safety, regulatory, physical, and other pertinent use information regarding a chemical.

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Neat - Undiluted.

NFPA - National Fire Protection Association (U.S.).

NIOSH - National lnstitute of Occupational Safety and Health, U.S. NIOSH is one of the sources cited when developing an OSHA MSDS.

NOEL - No Observed Effect Limit. The highest dose used in a toxicity test that produces no observed adverse effects.

Nonferrous - Any metal that is not based on iron, such as copper and aluminum.

Nonionic Surfactant - A surface-active agent that carries no complete electrical charge in solution. In metalworking fluids, they typically function as cleaners, emulsifiers, or lubricants.

NTP - National Toxicology Program, U.S. NTP is one of the reference sources used when developing an OSHA MSDS.

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Oil Emulsification - The property of a metalworking fluid that determines its capacity for emulsifying (absorbing) or dispersing oil.

OSHA - Occupational Safety and Health Administration, U.S. OSHA is one of the sources cited when developing an OSHA MSDS.

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PEL - Permissible Exposure Limit (OSHA) for a material for an 8 hour workday and 40 hour workweek. PELs are cited on the OSHA MSDS.

pH - The negative log of the hydrogen ion concentration of an aqueous solution expressed on a scale of 1 (acid) to 14 (alkaline). Neutral pH is 7.0.

Piercing - A operation of cutting internal features (holes or slots) in sheet stock. Often combined with blanking.

Polymer - A high molecular weight chemical compound consisting essentially of repeating structural units.

Positive Filter - A type of filter using some type of filtering material (paper, cloth, wire screen, etc.) to remove particulate from a metalworking fluid.

POTW - Publicly Owned Treatment Works (sewage).

PPM - Part Per Million

Precipitate - A reaction causing a solution to form an insoluble compound that settles to the bottom of the liquid. Also, the product of this process.

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QUV - A humdiity cabinet that uses accelerated means to simulate outdoor exposure to sunlight and weather.

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Ra - The average surface roughness computed as the arithmetic mean of the absolute value of the distance between the baseline to the maximum peak or valley height.

Rancidity - The condition in which a material has a foul or rank odor. In metalworking fluid mixes, rancidity is most often associated with high levels of bacteria.

RCRA - Resource Conservation and Recovery Act, administered by the EPA (U. S.). RCRA is one of the reference sources used when developing an OSHA MSDS.

Recycling - The process used to clean and restore a material for reuse.

Refractometer - An optical instrument that measures the refractive index of a liquid, such as a water-diluted metalworking fluid mix. The refractive index can be used to determine the concentration of a fresh, metalworking fluid mix.

REL - Recommended Exposure Limit for a material for a 10 hour workday and 40 hour workweek. RELs are cited on the OSHA MSDS.

Relative Humidity - The ratio of the amount of water vapor actually present in the air to the greatest amount possible at the same temperature

Residue - The material that is left by the metalworking fluid on the part, machine, or related items after the fluid flow stops.

Reverse Osmosis (RO) - A separation process similar to ultrafiltration, but using higher pressures and tighter semipermeable membranes. This reverses the natural process of osmosis causing water to flow from the more concentrated to the more dilute solution side of the membrane.

Rockwell - An indentation-type hardness test which uses a variety of indentors and loads.

RTECS - Registry of Toxic Effects of Chemical Substances, published by NIOSH. RTECS is one of the reference sources used when developing an OSHA MSDS.

Rust - A form of ferrous corrosion.

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SARA - Superfund Amendment and Reauthorization Act, U.S. SARA is one of the reference sources used when developing an OSHA MSDS.

SDF - Stamping and Drawing Fluid

Semisynthetic Fluid - A metalworking fluid with moderate to low content of mineral oil, usually 5% to 30%. Generally contains a significant amount of water, 30% to 60%. These fluids are sometimes called "preformed emulsions."

Soap - An emulsifier prepared by neutralizing a fatty acid with an alkaline material such as an amine or hydroxide.

Solid-Flim Lubricant - Solid lubricants, such as graphite or molybdenum disulfide.

Soluble Oil - A metalworking fluid with high oil content (50% to 80%) and little or no water content. As sold it consists solely of oil, emulsifiers, oil-soluble lubricants, corrosion inhibitors, etc. When mixed with water, it creates an emulsion that is milky in appearance.

Specific Gravity - The ratio of the mass of any volume of material to the mass of an equal volume of some reference material, usually water, at a standard temperature.

Specific Metal Removal Rate (Q') - The volume of metal removed per unit of time per unit of effective grinding wheel width.

STEL - Short-Term Exposure Limit for a material. A STEL, unless identified different, refers to a 15-minute time frame. STELs are cited on the OSHA MSDS.

STLE - Society of Tribologists and Lubrication Engineers

Sulfate - A salt resulting from neutralization of sulfuric acid, i.e. sodium sulfate (Na₂SO₄). High levels of sulfates are corrosive.

Sulfonate - Sulfonates can be used as emulsifiers and corrosion inhibitors. Sulfonates are can be produced both from oil and synthetically. Sulfonate are used in many products, i.e. metalworking fluids, soaps, cleaners, etc.

Surface Finish (or roughness) - Fine irregularities measured in terms of height and spacing.

Surfactant - A compound that reduces the surface tension of water.

SUS - Unit of viscosity (Saybolt universal seconds).

Swarf - Metal fines and grinding wheel particles generated during grinding.

Synthetic Fluid - A metalworking fluid that contains no mineral oil. Some synthetics are totally transparent while others are emulsions of synthetically derived lubricants (synthetic emulsions).

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TCLP - Toxicity Characteristics Leaching Procedure. Cited on the OSHA MSDS.

TDS - Total Dissolved Solids.

Thick Film Lubrication - A pressure film that is formed between moving surfaces that keeps them apart. This type of lubrication cannot easily be maintained in high-speed machinery. Used where reciprocating or oscillating conditions are low to moderate.

Thin Film Lubrication - A lubricating film that fills in the irregularities of the metal surfaces. The film thickness of the lubricant is such that the friction between the surfaces is determined by the properties of the surfaces as well as by the viscosity of the lubricant.

Titration - A procedure for determining volumetrically the concentration of a certain substance in a solution by adding a standard solution of known volume and strength until the reaction is complete. The endpoint is usually detected by a color change of an indicator solution or by an electrical measurement.

TLV - Threshold Limit Value. The limit of exposure to a material at or below which workers should experience no health problems (ACGIH).

TOC - Total Organic Carbon.

Tool Life - A measure of the length of time a tool will cut satisfactorily.

Total Oil - Is the percentage of all oil or oil-like material present in the metalworking fluid mix. This value includes both product oil and extraneous Oil. The Total Oil of a mix is usually determined by acidifying the mix and centrifuging.

Toxicology - The study of the health effects of chemical exposures.

Tramp Oil - That oil which is present in a metalworking fluid mix and is not from the product concentrate. The usual sources are machine tool lubrication systems leaks.

TSCA - Toxic Substances Control Act, U.S.

TWA - Time-weighted average.

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Ultraflitration (UF) - A separation technique in which a liquid is applied to a semipermeable membrane under moderate pressure. The liquid passing through the membrane (the "permeate") is cleaned and the waste stream (or "effluent") becomes more concentrated with dissolved solids.

UN Number - An identification number assigned by the United Nations to hazardous materials in transportation.

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Viscosity - The internal resistance to flow exhibited by a fluid.

Viscosity Index - A means of expressing the relationship between viscosity and temperature.

VOC - Volatile Organic Compounds.

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Waste Treatable - The ability to chemically or physically remove an additive from the water before disposing of the effluent.

Water hardness - The combined calcium and magnesium content of water. Usually expressed as parts per million (ppm) of calcium carbonate (CaCO₃). Each ppm of calcium contributes 2.5 ppm of hardness and each ppm of magnesium contributes 4.1 ppm of hardness.

Wear - Loss of material from a surface due to rubbing.

Wetting Agent - An additive which reduces surface and interfacial tension of a fluid and makes possible the spreading of the fluid over a surface.

WHMIS - Workplace Hazardous Materials Information System (Canada). A WHMIS MSDS is the Canadian version of an OSHA MSDS.

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Yeast - Mostly single-celled fungi. They are larger than bacteria and are either round or oval in shape.

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