Acidity or Acid Number - In lubricants, acidity denotes the presence of acid-type constituents (may be oxidation by-products or related to additive components) whose concentration is usually defined in terms of acid number.  (See also Total Acid Number.)


Acid Split - A concentration test conducted on a water-based metalworking fluid by breaking the emulsion and measuring the total oil content.


Additive - A chemical compound or compounds added to a lubricant with the purpose of improving the existing properties of base materials or fluids.


AGMA - The American Gear Manufacturers Association is a voluntary association of companies, consultants, and academicians with a direct interest in the design, manufacture, and application of gears, couplings, and related power transmission components and equipment.


Air Entrainment - Air may be entrained in a liquid through mechanical means and/or by release of dissolved air due to a sudden change in pressure.


Alkalinity - A measure of concentration performed by quantifying the alkaline components of a fluid.


Ambient Temperature - Temperature of the area or atmosphere around a process, (not the operating temperature of the process itself).


Anhydrous - no water is present.


ANSI - American National Standards Institute


Anti-foam Agent - An additive used to control foam.


Anti-friction Bearing - A rolling type bearing in which the rotating or moving member is supported or guided by means of ball, cylinders or other rolling elements. Friction is reduced, not totally eliminated.


Antioxidant - A compound added to a lubricant used to combat the action of oxidation.


Antiwear Agents - Reduce friction, wear, and scoring under certain conditions of boundary lubrication. May or may not combine chemically with metal surfaces. Lubricating solids provide anti-wear protection without chemically altering work surfaces.


API - The American Petroleum Institute (API) is the national trade association that represents all aspects of America's oil and natural gas industry. Provides extensive publication and information services, conducts fundamental research on petroleum, and maintains a library of several thousand volumes.


API Gravity - Measured by ASTM D-287 or ASMD-1298. A density scale established by the API and in general use in the petroleum industry, the unit being called the "API degree". This unit is defined in terms of specific gravity as follows:


    Degrees API = [141.5 / specific gravity (60°F/60°F)] - 131.5

ASTM - American Society for Testing Materials. Engineers, scientists, and skilled technicians hold memberships as individuals or as representatives of business firms, government agencies, educational institutions, and laboratories. Established voluntary consensus standards for materials, products, systems, and service. Developed thousands of standard test methods, specifications, and recommended practices now in use.


Autoignition Temperature - Temperature where a material combusts without source of ignition at standard pressure and atmosphere.


Axial Load Bearing - A bearing in which the load acts in the direction of the axis rotation.


Bacterial Count - A test to determine the approximate bacteria levels in a fluid, typically performed on a water based metalworking fluid using a dipslide.


Ball Bearing - An anti-friction bearing comprising of rolling elements in the form of balls or spheres.


Base Stock - Fully refined lube oil, broadly defined by API Group Numbers and used to formulate fluid lubricants and greases.


Bearing - A device which provides support or guide whereby a moving part such as a shaft or axle is positioned with respect to the other parts of a mechanical device.


Boundary Lubrication - A condition of lubrication in which partial contact takes place between the mating surfaces; the bulk viscosity characteristics of the lubricant do not apply.


Bright Stock - Refined, high viscosity base oils of API Group I, can be paraffinic or naphthenic, usually made from residual stocks by refining processes, which may include a combination of solvent extraction, propane de-asphalting or catalytic de-waxing.


By-Pass Filtration - Sometimes called dialysis filtration or kidney loop filtration where a filter system processes only a portion of the total flow of circulating fluid system, passes through a filter. These systems usually have their own circulating pump operating in parallel to the main flow.


Centipoise (cP) - A standard unit of absolute (dynamic) viscosity. Water has a viscosity of 1 cP at 20°C.

    cP = cSt * Specific Gravity

Centistoke (cSt) - ISO standard unit of kinematic viscosity with a unit of measure of mm2/sec.

    cSt = cP / Specific Gravity

Cast Iron Corrosion Test (CIC Test) - A test to determine the rust preventive qualities of a water dilutable metalworking fluid.


Chloride - A negatively charged chlorine atom commonly found in water and may be monitored in water based metalworking fluids, as high levels can lead to corrosion of machines and parts.


Chlorine or Chlorinated Paraffin - A common extreme pressure additive used in metalworking fluids. Due to EPA concerns some manufacturers have eliminated this material from their offerings.


Circulating Lubrication - A system of lubrication in which the lubricant, typically a fluid lubricant, after having passed through a bearing or group of bearings or gear train, is recirculated by means of a pump.


Cleveland Open Cup (COC) - See Flash Point, Fire Point. (ASTM D-92)


Cloud Point - The temperature at which paraffin wax or wax crystals become solid and begin to crystallize or separate from the solution, imparting a cloudy appearance to the fluid when chilled (ASTM Method D 2500, ASTM D-5772 and ASTM D-5773).


Coefficient of Friction (COF) - The coefficient of friction (also called COF, or friction) is a measurement of the force it takes to slide an object across another surface divided by the object's weight.


Compounding - The addition of fatty oils and similar materials to lubricants to impact special properties. These materials are typically used as lubricity agents in Worm Gear Oils and Steam Cylinder Oils. Lubricants to which such materials have been added are known as compounded oils.


Conradson Carbon Residue Test - Determines the percentage weight of carbonaceous residue when a sample is heated in an ASTM standard procedure. Carbon-forming properties of lubricating oils for use in applications such as air compressors can be an important factor in the choice of a suitable lubricant. In such applications, the formation of carbon deposits can be very troublesome.


Copper Strip Corrosion - A measure of the activity of a lubricant towards copper or copper based alloys, typically measured by ASTM D-130 or ASTM D-4048. It is the chemical attack of copper surfaces as the result of oxidation or other chemical action. Acids or other corrosive agents cause it.


Corrosion - The attrition or wearing away of a substance by acid or electrochemical action.


Demulsibility - The ability of an oil to separate from water, metalworking fluids or process fluids where mixing can occur. Its measure usually details oils, water and emulsion in some scale related to a time factor. Demulsibility is sometimes expressed as the rate, in cubic centimeters per hour, or settling out of a fluid from an emulsion under specified conditions.


Density - The mass of a unit volume of a material. It can be measured in several ways including ASTM D-1298 and its numerical value varies with the units used.


Dermatitis - An inflammatory response of the skin due to exposure to certain chemicals which may be reversed when exposure ceases. Signs and symptoms vary greatly.


Diester Oil - A synthetic lubricating liquid made from esters; also called ester oil. This is part of the ester family of fluids; other members include Polyol esters and Phosphate esters.


DIN - Deutsche Industrie Norman - German equivalent of ASTM.


DI Water - Deionized water. Water which has been treated to remove dissolved ionic salts (i.e. hardness ions) to purify it.


DN Factor - (also called speed factor) Determined by multiplying the bearing pitch diameter dm (measured in mm), by the speed, N, of the journal (measure in RPM). Together with operating temperature, DN is used to help determine the appropriate oil viscosity for lubricating bearings.

    DN = dm (in mm) * N (in RPM) where dm = (I.D. + O.D.)/2

Dropping Point - The temperature at which grease passes from a semi-solid to a liquid state (actually when the thickener begins to release oil on heating). Dropping point helps to determine the maximum temperature at which a grease will lubricate and remain in a bearing without running out.


Dynamic Viscosity - See Absolute Viscosity


Elastohydrodynamic Lubrication (EHD) - Lubrication modified to take into consideration the elastic properties of the bearing material and the viscosity increase of the lubricant under concentrated load or pressure.


Emulsifier - A chemical used to promote the emulsification of two liquids and to enhance the stability of the emulsion.


Emulsion - A mechanical mixture of the two immiscible liquids such as oil and water. Water-in-oil emulsions have water as the non-continuous phase and oil as the continuous phase. Oil-in-water emulsions have the water as the continuous and oil as the non-continuous phase.


EP - Extreme Pressure


EP Additives - Per AGMA, these are now known as Anti-Scuffing additives. Reduce friction, wear, and scoring under certain conditions of boundary lubrication. Chemical EP additives are more or less corrosive depending on type and actual conditions of service. Lubricating solids, such as Castrol's Tribol Gear Oil Additive (TGOA) and Micro Flux Trans (MFT) can provide EP characteristics without corrosive chemical action in a non-sacrificial manner.


EP Lubricants - Lubricants that have been fortified with additives that appreciably increase the load carrying properties of the base lubricant, as defined by AGMA or other agency, thus reducing excessive wear. These additives may be based on liquid or soluble chemistries, solids or combinations, thereof.


Falex Wear & EP Test - Determines the extreme pressure (EP) and anti-wear properties of oil or grease. Clamped between tow VEE blocks, a standard Test Pin is rotated while load is applied. Falex wear is done by subjecting a lubricant to a constant test load (ex: 350 or 700lbs Force) for 15 minutes. The number of teeth advanced on the standard loading gear (ratchet wheel) in order to maintain the test load is a measure of wear. Note: It has been found that 1 tooth advance is equivalent to 0.000056 inch of wear. Falex EP test is done by subjecting a lubricant to increasing load until failure occurs as indicated by high torque/temperature, seizure and/or breakage of the test pin or shear pin.


Film Strength - The property of an oil (sometimes defined as cohesiveness, ie.e the oil film's ability to remain as continuous) which enables it to maintain an unbroken film on lubricated components during operations. Rupture of the film could result in scuffing or scoring of the surfaces.


Filter - Any device, media or porous material use to remove particulate matter from fluids. Filters may be inline with other components such as pumps and circulation equipment or "kidney lube" design. 


Fire Point - Continuation of the Flash Point test which measures the lowest temperature at which a fluid gives off sufficient vapors to burn for at least 5 seconds when a small flame is passed over the surface of the sample.


Flash Point (COC) (Cleveland Open Cup Test) - This ASTM D-92 test determines the lowest temperature at which a fluid gives off sufficient vapors to ignite, but not continue burning, when a small flame is passed over the surface of the sample.


Flash Point Test (Tag Closed-Cup Tester) - A method of test, ASTM D-56, for the determination of the flash point of liquid fields or solvents flashing below 175° F, with the exception of fuel oils.


Foam - A froth produced by mechanical action that introduces air into a lubricant. 


Four-Ball EP Test - This test is made with four steel balls arranged in the form of Equilateral Tetrahedron (pyramid). The result determines the EP characteristics of lubricants by means of a load scar measured in mm and a weld point measured in kgf. Evaluates wear preventive properties under much higher unit loads than the FOUR BALL WEAR TEST.


Fretting - The removal of extremely fine particles by the action of adhesive forces between bearing surfaces. Occurs when bearings are subjected to slight but continued vibrations. Often called fretting corrosion or false brinelling.

Friction - The force that must be overcome at the common boundary between two bodies when, under the action of an external force, one body moves or tends to move over the surface of the other. 


FZG Test - Four Square Gear Test defined by ASTM D-5182 and DIN 51354; a German gear test for evaluation EP properties. 


Gravity - Used the define the density of a fluid, semi-fluid or solid material. See Specific Gravity, API Gravity. 


Grease - Greases are made from a lubricating fluid and a thickener. The fluid may be petroleum, synthetic, or some combination. The thickener is often a "soap", the common name for the metallic salt of a fatty acid. The soap can be thought of as holding the oil like a sponge holds water. Lubrication is provided by a gradual release of the fluid from the soap structure. Some greases also use "non-soap" thickeners. 


H1 - National Sanitary Foundation (NSF), previously USDA, code for lubricants acceptable for use where incidental contact with food products may occur. These compounds cannot be used as Food Additives. Formerly AA.


H2 - National Sanitary Foundation (NSF), previously USDA, code for lubricants acceptable for use in food facilities where there is no possible contact with the food. Formerly BB.


Hardness - Measurement of calcium and magnesium present in water and water-based metalworking fluids and often reported in ppm or gpg (grains per gallon CaC03).


Hydrocarbon - A compound containing hydrogen and carbon. Molecules with up to approximately four carbons, the simplest hydrocarbons are gases at room temperature; but as the number of carbons increase (increasing molecular weight), they change to the liquid form and, finally, to the solid state. They form the primary constituents of petroleum. 


Hydrodynamic Lubrication - Lubrication where the components are fully separated by a fluid film. Sometimes defined as a system of lubrication in which the shape and relative motion of the sliding surfaces causes the formation of a fluid film having sufficient pressure to separate the surfaces. 


ISO - Internation Standards Organization. For example, ISO devised a viscosity grading system which specifies the viscosity ranges of industrial oils. ISO is an international body with a membership of over 50 countries- including USA, Russia, UK, France, Germany, Italy, Sweden and Japan.

ISO Viscosity Grade System - A classification, ASTM D-2422, for individual lubricants based on mm2/sec viscosity at 40°C. Covers eighteen grades from 1 to 1500 centistokes. 


Journal Bearing - A bearing which relies on fluid film, having no rolling elements, for rotational or linear movement. Sometimes descried as a sliding type of bearing in conjunction with which a journal or slide operates. They may be described as full or partial sleeve bearings or as plain bearings. 


Kinematic Viscosity - Measured by rate of flow through capillary tubes which permit highly accurate measurements. Measured in mm2/sec, also known as centistokes, kinematic viscosity has worldwide application and is measured at standard Fahrenheit and Celsius temperatures. 


Load Wear Index (LWI) - See Four-Ball Test; a measure of the relative ability of a lubricant to prevent wear under applied loads. This value is expressed in units of kilogram force (kgf) and is calculated from the loads applied and corrected for elastic deformation of the balls under static loading and for the size of the wear scar. Formerly called Mean Hertz Load. 


Lubricant - Any material or substance interposed between two surface sin relative motion for the purpose of reducing friction, carrying away heat and contaminants between them. 


Lubricity - A moderate load-carrying ability above anticipated service capacity indicated by viscosity. Lubricity can be enhanced by additives or compounding.


Metal Deactivator - An additive used in lubricants and fuels that converts into an inactive form, the traces of metal (such as copper in fuels or component parts) and metal surfaces (such as copper in gear, bearing and other components). This trace metal, in the absence of the activator, would catalyze gum formation and other oxidation.


MFT - Micro Flux Trans is a patented proprietary additive system that provides superior friction reduction and surface improvement characteristics that works without sacrificing component surfaces. Sometimes referred too as Plastic Deformation technology. 


Mineral Oil - Oils derived from a mineral source, such as petroleum crude oil, as opposed to oils derived rom plants and animals. 


Multigrade Oil - API specifications that define performance at 2 different operating conditions such as 0°C and 100°C, typically for crankcase and gear oils. An oil that meets the low temperature viscosity limits of one of the SAE "W" numbers as well as the 100°C viscosity limits of one of the non-winter grades.


Naphthenic Base Oils - A characterization of certain petroleum products prepared from Naphthenic type crudes (crudes contains high percentage of ring type hydrocarbon molecules as opposed to linear or branched molecules). 


Neutralization Number - Sometimes called "Neut Number" or Acid Number, ASTM D-664 or ASTM D-974, is a term still used in the petroleum industry, but rapidly becoming obsolete in the lubrication field. See Total Acid Number. 


Neutral Oil - Light overhead cuts of lubricants stocks. Neutral oils are the basis for most commonly used automotive lubricants and resemble Paraffinic oils in basic properties. 


NLGI - Formerly called National Lubrication Grease Institute. Professional association of companies manufacturing or marketing all types of lubrication greases, suppliers of such companies, and technical and educational organizations. Promotes research and testing for the development of better lubricating greases and better grease lubrication engineering service to industry, collects, and disseminates technical data, and conducts forums. 


NLGI Penetration Number - A physical test (ASTM D-217) established by the NLGI to define the consistency (softens or hardness) of a grease at 25°C/77°F. A specialized instrument, known as a penetrometer, is used to measure the depth in tenths of a millimeter that a standard cone will penetrate when dropped freely on a grease sample for 5 seconds under prescribed conditions. Softer greases have higher penetration number while harder ones have lower. Penetrations are generally made on grease which has been worked a specified number of double strokes in a grease working device. Worked penetration represent 60 double strokes unless otherwise noted. Similar measurements, called unworked penetration, are sometimes made on greaser that has not been worked.


OEM - Original Equipment Manufacture. 


Oxidation - The chemical combination of oxygen with organic material. At room temperature petroleum oil oxidizes slowly, but at high temperatures oxidation proceeds rapidly. Over time, severe oxidation forms acid and sludge and increases oil viscosity.


Oxidation Stability - Typically measured by ASTM D-943, ASTM D-942, ASTM D-2272 or ASTM D-2893 and other methods to determine a lubricant's ability to resist natural degradation upon contact with oxygen, heat, and other catalysts. 


Paraffinic Base Oil - A characterization of certain petroleum products prepared from Paraffinic type crudes (crudes containing a high percentage of straight chain aliphatic hydrocarbon molecules and also called Neutral Oils). Lubricating oils made from these crudes are normally distinguished from similar oils from other crudes (both oils equally well refined) by higher API gravity and higher viscosity index (VI).


pH - A measure from 0-14 of the relative acidity or alkalinity of a water-base system. pH of 7 is neutral. pH above 7 is alkaline. pH below 7 is acidic.


Plain Bearing - Any simple sliding type bearing as distinguished from tapered land, tilting pad, or anti-friction bearing, etc. where there is essentially a journal and a shell.


Polar Molecules - Non-symmetrical distribution of natural forces within certain molecules gives them properties similar to a magnet. Can bond in a nondestructive way to metal to protect surfaces or reduce friction.


Pour Point - Measured by ASTM D-93; the pour point of a lubricant is the lowest temperature at which the lubricant will pour or flow when it is chilled without disturbance under specified circumstances.


Pour Point Depressant - An additive, usually polymeric, that retards wax crystallization, and lowers the pour point.


R&O - A description of a fluid that contains inhibitors that work to reduce Rust and Oxidation.


Refractometer - Common handheld instrument for measuring the concentration of water-based metalworking fluids. Measures the refractive index (Brix) of the solution based on light bending as a result of the solids content. The Brix concentration must be multiplied by the refractometer factor of the fluid to get actual concentration. Each fluid may have its own unique refractometer factor which can be obtained from the fluid manufacturer.

    Concentration = Brix * Refract Factor of Coolant

RO Water - Reverse Osmosis. Use of a membrane to remove charged ions (i.e. hardness) from water to purify it.


Roller Bearing - An anti-friction bearing comprising rolling elements in the form of rollers.


RPVOT - Measured by ASTM D-2272, Rotary Pressure Vessel Oxidation Test, also known as RBOT (Rotary Bomb Oxidation Test) is an accelerated laboratory evaluation method to compare oxidation life of lubricants in similar formulations for hydraulic oils, turbine oils, transformer oils and gear oils.


Rust Prevention Test - A test for determining the ability of an oil to aid in preventing the rusting of ferrous parts in the presence of water or synthetic sea water.


SAE - Society of Automotive Engineers. Professional society of engineers in the field of self-propelled ground, flight, and space vehicles. To promote the arts, construction, and utilization of self-propelled mechanisms, prime movers, components thereof, and related equipment.


SAE Viscosity Number - System for classifying crankcase, transmission, and differential lubricants, according to their viscosities, established by the Society of Automotive Engineers. SAE numbers are used in connection with recommendations for crankcases oils to meet various design, service and temperature requirements affecting viscosity; they do not denote quality.


Saybolt Universal Seconds (Viscosity) - Measured in seconds (SUS or SSU) of time required for a fixed volume to flow through a standard tube. Typical test temperatures are 100°F and 210°F.


Semi-Synthetic Fluid - With oils, this refers to a combination of synthetic oil with mineral oil to create a hybrid which is higher performing than mineral oil but less expensive than synthetic oil. With metalworking fluids, this refers to oil-containing water-based coolants which form tight emulsions and have better life and bacteria resistance than traditional soluble oils.


Sleeve Bearing - A journal bearing, usually a full journal bearing.


Soluble Oil - Water-based metalworking fluid produced by mixing mineral oil with emulsifiers and other additives. These are typically less expensive, older technology fluids as compared to modern semi-synthetic coolants.


Specific Gravity - Can be measured by a number of methods to determine the ratio of the weight in air of a given volume of a material to the weight in air of an equal volume of water at a stated temperature.


Splash Lubrication - A system of lubrication in which parts of a mechanism dip into and splash lubricant onto themselves and/or parts of the mechanism.


SRV Test - Tribological test that measures the EP and Wear characteristics of a lubricant in a controlled manner. The test rig is quite flexible allowing changes in the way load, temperatures, movement etc. can be changed and parameters / results are recorded.


STLE - Society of Tribologists and Lubrication Engineers. Engineers and others engaged in the technological development and use of lubricants, lubricating equipment, and lubrication systems.

Surfactant - Surface tension reduction additive. 


SUS - Saybolt Universal Seconds, sometimes reported as Saybolt Seconds Universal (SSU). See also VISCOSITY.


Synthetic Hydrocarbon - Oil molecule prepared by reacting Paraffinic materials. Known as PAO (Poly Alpha Olefins) or SHC (Synthetic Hydro Carbons).


Synthetic Lubricant - A man-made lubricant produced by either chemical synthesis or refining processes from materials not naturally occurring in crude oil.


Synthetic Coolant - Water-based metalworking fluid which contains no oil and creates a clear solution with water.


Tackifier - An extremely sticky polymer based additive, added to slipway oils and other lubricants so they stick physically to surfaces.


TGOA - Tribol Gear Oil Additive is Castrol's patented proprietary additive system that provides superior friction reduction and surface improvement characteristics that works without sacrificing component surfaces. Sometimes referred to as Plastic Deformation technology.


Timken EP Test (Timken OK Load Test) - This test is made with a steel test cup (ring) rotating against a loaded steel block and lubricated by the test fluid. Ten minute tests are run at increasing loads (5lbs increment) until the maximum load is obtained with no visual evidence of welding or seizing.


TOST - Turbine Oil Oxidation Stability Test, ASTM D-943, used on turbine, hydraulic, and other circulating oils to determine oxidation resistance in number of hours.


Total Acid Number (TAN) - The quantity of base, expressed in terms of the equivalent number of milligrams of potassium hydroxide (KOH), that is required to titrate the strong base constituents present in 1g of sample (ASTM Method D 664 or D 974).


Total Base Number (TBN) - This is a "back-titration" used to measure the reserve alkalinity in fluids, such as Diesel engine oils. The quantity of base, expressed in terms of the equivalent number of milligrams of potassium hydroxide, which is required to titrate the strong base constituents present in 1g of sample (ASTM Method D 664 or D 974).


Tramp Oil - Unwanted oil that becomes mixed with metalworking fluids, such as hydraulic and slipway oil.

Tribology - The science and engineering of interacting surfaces in relative motion. Includes the study and application of the principles of friction, lubrication and wear. Tribologists are people who work in this field. Peter Jost first coined the phrase tribology.


Viscosity - Measure of a liquid's resistance to flow at specified temperatures.


Viscosity Grade - Any of a number of systems that characterize lubricants according to viscosity for particular applications, such as industrial oils, gear oils, automotive engine oils, automotive gear oils, and aircraft position engine oils. ISO grades are most common in industrial applications (i.e. ISO 32, 46, 68, 100, 150, 220, 320, 460, 680, etc.).


Viscosity Index (VI) - A measure of the viscosity-temperature characteristics of an oil, indicating the rate at which the viscosity of the oil will change as temperature increases or decreases. Viscosity Index does not necessarily indicate the quality of an oil. In general, viscosity index is only significant where large temperature variations are encountered.


Viscosity Index Improver - Additive that increases lubricant viscosity index (VI), usually required for formulation of multi-grade engine oils and other lubricants designed for wide temperature ranges.


VOC - Volatile Organic Compound. A carbon containing substance that evaporates. The VOC value of a chemical indicates the degree of chemical evaporation to the atmosphere.


White Oils - Light-colored and usually highly refined mineral oils usually employed in medicinal and pharmaceutical preparations, and as a base for creams, salves, and ointments, but also used as lubricants mostly found in food grade products. Typically defined by USP (United States Pharmacopeia) standards and are used in food-grade formulations.