Cutting fluid is a type of
coolant
A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosio ...
and
lubricant
A lubricant (sometimes shortened to lube) is a substance that helps to reduce friction between surfaces in mutual contact, which ultimately reduces the heat generated when the surfaces move. It may also have the function of transmitting forces, t ...
designed specifically for
metalworking
Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale ...
processes, such as
machining
Machining is a process in which a material (often metal) is cut to a desired final shape and size by a controlled material-removal process. The processes that have this common theme are collectively called subtractive manufacturing, which utilizes ...
and stamping. There are various kinds of cutting fluids, which include oils, oil-water
emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
s, pastes, gels, aerosols (mists), and air or other gases. Cutting fluids are made from petroleum distillates,
animal fat
Animal fats and oils are lipids derived from animals: oils are liquid at room temperature, and fats are solid. Chemically, both fats and oils are composed of triglycerides. Although many animal parts and secretions may yield oil, in commercial p ...
s,
plant oil
Plant oils or vegetable oils are oils derived from plant sources, as opposed to animal fats or petroleum. There are three primary types of plant oil, differing both the means of extracting the relevant parts of the plant, and in the nature of the ...
s, water and air, or other raw ingredients. Depending on context and on which type of cutting fluid is being considered, it may be referred to as cutting fluid, cutting oil, cutting compound, coolant, or lubricant.
Most metalworking and machining processes can benefit from the use of cutting fluid, depending on workpiece material. Common exceptions to this are
cast iron
Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
and
brass
Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...
, which may be machined dry (though this is not true of all brasses, and any machining of brass will likely benefit from the presence of a cutting fluid).
The properties that are sought after in a good cutting fluid are the ability to:
* Keep the workpiece at a stable temperature (critical when working to close
tolerances). Very warm is acceptable, but extremely hot or alternating hot-and-cold are avoided.
* Maximize the life of the cutting tip by lubricating the working edge and reducing
tip welding.
* Ensure safety for the people handling it (toxicity, bacteria, fungi) and for the environment upon disposal.
* Prevent rust on machine parts and cutters.
Function
Cooling
Metal cutting generates
heat
In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...
due to friction and energy lost deforming the material. The surrounding air has low
thermal conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa.
Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal ...
(conducts heat poorly) meaning it is a poor coolant. Ambient air cooling is sometimes adequate for light cuts and low duty cycles typical of
maintenance, repair and operations
The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure, and supporting utilities in industrial, business, and residential install ...
(MRO) or hobbyist work. Production work requires heavy cutting over long time periods and typically produces more heat than air cooling can remove. Rather than pausing production while the tool cools, using liquid coolant removes significantly more heat more rapidly, and can also speed cutting and reduce friction and tool wear.
However, it is not just the tool which heats up but also the work surface. Excessive temperature in the tool or work surface can ruin the
temper
Temper, tempered or tempering may refer to:
Heat treatment
* Tempering (metallurgy), a heat treatment technique to increase the toughness of iron-based alloys
** Temper mill, a steel processing line
* Tempering (spices), a cooking technique where ...
of both, soften either to the point of uselessness or failure, burn adjacent material, create unwanted
thermal expansion
Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions.
Temperature is a monotonic function of the average molecular kinetic ...
or lead to unwanted chemical reactions such as
oxidation
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
.
Lubrication
Besides cooling, cutting fluids also aid the cutting process by lubricating the interface between the tool's cutting edge and the chip. By preventing friction at this interface, some of the heat generation is prevented. This lubrication also helps prevent the chips from being welded onto the tool, which would interfere with subsequent cutting.
Cutting fluids may also assist in reducing cutting forces through the
Rehbinder effect The Rehbinder effect in physics is the reduction in the hardness and ductility of a material, particularly metals, by a surfactant film.
A proposed explanation for this effect is the disruption of surface oxide films, and the reduction of surface e ...
.
Extreme pressure additive 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 additi ...
s are often added to cutting fluids to further reduce tool wear.
Delivery methods
Every conceivable method of applying cutting fluid (e.g., flooding, spraying, dripping, misting, brushing) can be used, with the best choice depending on the application and the equipment available. For many metal cutting applications the ideal has long been high-pressure, high-volume pumping to force a stream of liquid (usually an oil-water emulsion) directly into the tool-chip interface, with walls around the machine to contain the splatter and a sump to catch, filter, and recirculate the fluid. This type of system is commonly employed, especially in manufacturing. It is often not a practical option for maintenance, repair and overhaul or hobbyist metalcutting, where smaller, simpler machine tools are used. Fortunately it is also not necessary in those applications, where heavy cuts, aggressive
speeds and feeds
The phrase speeds and feeds or feeds and speeds refers to two separate velocities in machine tool practice, cutting speed and feed rate. They are often considered as a pair because of their combined effect on the cutting process. Each, however, ...
, and constant, all-day cutting are not vital.
As technology continually advances, the flooding paradigm is no longer always the clear winner. It has been complemented since the 2000s by new permutations of liquid, aerosol, and gas delivery, such as minimum quantity lubrication and through-the-tool-tip cryogenic cooling (detailed below).
Through-tool coolant systems, also known as through-spindle coolant systems, are systems plumbed to deliver coolant through passages inside the spindle and through the tool, directly to the cutting interface. Many of these are also high-pressure coolant systems, in which the operating pressure can be hundreds to several thousand
psi
Psi, PSI or Ψ may refer to:
Alphabetic letters
* Psi (Greek) (Ψ, ψ), the 23rd letter of the Greek alphabet
* Psi (Cyrillic) (Ѱ, ѱ), letter of the early Cyrillic alphabet, adopted from Greek
Arts and entertainment
* "Psi" as an abbreviatio ...
(1 to 30
MPa
MPA or mPa may refer to:
Academia
Academic degrees
* Master of Performing Arts
* Master of Professional Accountancy
* Master of Public Administration
* Master of Public Affairs
Schools
* Mesa Preparatory Academy
* Morgan Park Academy
* Mound ...
)—pressures comparable to those used in
hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
circuits. High-pressure through-spindle coolant systems require
rotary union
A rotary union is a union that allows for rotation of the united parts. It is thus a device that provides a seal between a stationary supply passage (such as pipe or tubing) and a rotating part (such as a drum, cylinder, or spindle) to permit the f ...
s that can withstand these pressures.
Drill bit
Drill bits are cutting tools used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order ...
s and
endmill
An end mill is a type of milling cutter, a cutting tool used in industrial milling applications. It is distinguished from the drill bit in its application, geometry, and manufacture. While a drill bit can only cut in the axial direction, most m ...
s tailored for this use have small holes at the lips where the coolant shoots out. Various types of
gun drill
Gun drills (through coolant drill) are straight fluted drills which allow cutting fluid (either compressed air or a suitable liquid) to be injected through the drill's hollow body to the cutting face. They are used for deep hole drilling—a ...
s also use similar arrangements.
Types
Liquids
There are generally three types of liquids: mineral, semi-synthetic, and synthetic. Semi-synthetic and synthetic cutting fluids represent attempts to combine the best properties of oil with the best properties of water by suspending emulsified oil in a water base. These properties include: rust inhibition, tolerance of a wide range of water hardness (maintaining pH stability around 9 to 10), ability to work with many metals, resist thermal breakdown, and environmental safety.
Water is a good conductor of heat but has drawbacks as a cutting fluid. It boils easily, promotes rusting of machine parts, and does not lubricate well. Therefore, other ingredients are necessary to create an optimal cutting fluid.
Mineral oil
Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils.
The name 'mineral oil' by itself is imprecise, ...
s, which are petroleum-based, first saw use in cutting applications in the late 19th century. These vary from the thick, dark, sulfur-rich cutting oils used in heavy industry to light, clear oils.
Semi-synthetic coolants, also called ''soluble oil'', are an emulsion or
microemulsion Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be ...
of water with mineral oil. In workshops using British English soluble oil is colloquially known as SUDS. These began to see use in the 1930s. A typical CNC machine tool usually uses emulsified coolant, which consists of a small amount of oil emulsified into a larger amount of water through the use of a detergent.
Synthetic coolants originated in the late 1950s and are usually water-based.
The official technique to measure oil concentration in cutting fluid samples is manual
titration
Titration (also known as titrimetry and volumetric analysis) is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified analyte (a substance to be analyzed). A reagent, termed the ''titrant'' ...
: 100ml of the fluid under test is titrated with a 0.5M HCl solution to an endpoint of pH 4 and the volume of titrant used to reach the endpoint is used to calculate the oil concentration. This technique is accurate and not affected by fluid contamination, but needs to be performed by trained personnel in a laboratory environment. A hand-held
refractometer
A refractometer is a laboratory or field device for the measurement of an Refractive index, index of refraction (refractometry). The index of refraction is calculated from the observed refraction angle using Snell's law. For mixtures, the index ...
is the industrial standard used to determine the mix ratio of water-soluble coolants that estimates oil concentration from the sample refractive index measured in the
Brix scale
Degrees Brix (symbol °Bx) is a measure of the dissolved solids in a liquid, and is commonly used to measure dissolved sugar content of an aqueous solution. One degree Brix is 1 gram of sucrose in 100 grams of solution and represents the strengt ...
. The refractometer allows for in situ measurements of oil concentration within industrial plants. However, contamination of the sample reduces the accuracy of the measure. Other techniques are used to measure the oil concentration in cutting fluids, such as measure of the fluid
viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
,
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
, and
ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
speed. Other test equipment is used to determine such properties as acidity and conductivity.
Others include:
*
Kerosene
Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...
and
rubbing alcohol
Rubbing alcohol is either an isopropyl alcohol or an ethanol-based liquid, with isopropyl alcohol products being the most widely available. The comparable ''British Pharmacopoeia'' (''BP'') is surgical spirit. Rubbing alcohol is denatured and un ...
often give good results when working on
aluminum
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It has ...
.
*
WD-40
WD-40 is an American brand and the trademark of a penetrating oil manufactured by the WD-40 Company based in San Diego, California. The formula for WD-40 was invented for the Rocket Chemical Company as early as 1953 before it evolved into the ...
and
3-In-One Oil work well on various metals. The latter has a citronella odor; if the odor offends, mineral oil and general-purpose lubricating oils work about the same.
* Way oil (the oil made for machine tool ways) works as a cutting oil. In fact, some screw machines are designed to use one oil as both the way oil and cutting oil. (Most machine tools treat way lube and coolant as separate things that inevitably mix during use, which leads to tramp oil skimmers being used to separate them back out.)
*
Motor oil
Motor oil, engine oil, or engine lubricant is any one of various substances used for the lubrication of internal combustion engines. They typically consist of base oils enhanced with various additives, particularly antiwear additives, deterg ...
s have a slightly complicated relationship to machine tools. Straight-weight non-detergent motor oils are usable, and in fact SAE 10 and 20 oils used to be the recommended spindle and way oils (respectively) on manual machine tools decades ago, although nowadays dedicated way oil formulas prevail in commercial machining. While nearly all motor oils can act as adequate cutting fluids in terms of their cutting performance alone, modern multi-weight motor oils with detergents and other additives are best avoided. These additives can present a copper-corrosion concern to brass and bronze, which machine tools often have in their bearings and leadscrew nuts (especially older or manual machine tools).
*
Dielectric
In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...
fluid is used as a cutting fluid in
electrical discharge machines (EDMs). It is usually
deionized water
Purified water is water that has been mechanically filtered or processed to remove impurities and make it suitable for use. Distilled water was, formerly, the most common form of purified water, but, in recent years, water is more frequently puri ...
or a high-
flash-point
The flash point of a material is the "lowest liquid temperature at which, under certain standardized conditions, a liquid gives off vapours in a quantity such as to be capable of forming an ignitable vapour/air mixture". (EN 60079-10-1)
The fl ...
kerosene. Intense heat is generated by the cutting action of the electrode (or wire) and the fluid is used to stabilize the temperature of the workpiece, along with flushing any eroded particles from the immediate work area. The dielectric fluid is non-conductive.
* Liquid (water or petroleum oil) cooled water tables are used with the plasma arc cutting (PAC) process.
*
Neatsfoot oil
Neatsfoot oil is a yellow oil rendered and purified from the shin bones and feet (but not the hooves) of cattle. "Neat" in the oil's name comes from an Old English word for cattle. Neatsfoot oil is used as a conditioning, softening and preserva ...
of the highest grade is used as a lubricant. It is used in metalworking industries as a cutting fluid for aluminum. For machining, tapping and drilling aluminum, it is superior to
kerosene
Kerosene, paraffin, or lamp oil is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from el, κηρός (''keros'') meaning "wax", and was regi ...
and various water-based cutting fluids.
Pastes or gels
Cutting fluid may also take the form of a paste or gel when used for some applications, in particular hand operations such as
drill
A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driverchuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to ...
ing and
tapping
Tapping is a playing technique that can be used on any stringed instrument, but which is most commonly used on guitar. The technique involves a string being fretted and set into vibration as part of a single motion. This is in contrast to stand ...
. In sawing metal with a
bandsaw
A bandsaw (also written band saw) is a power saw with a long, sharp blade consisting of a continuous band of toothed metal stretched between two or more wheels to cut material. They are used principally in woodworking, metalworking, and lumb ...
, it is common to periodically run a stick of paste against the blade. This product is similar in form factor to lipstick or beeswax. It comes in a cardboard tube, which gets slowly consumed with each application.
Aerosols (mists)
Some cutting fluids are used in
aerosol
An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...
(mist) form (air with tiny droplets of liquid scattered throughout). The main problems with mists have been that they are rather bad for the workers, who have to breathe the surrounding mist-tainted air, and that they sometimes don't even work very well. Both of those problems come from the imprecise delivery that often puts the mist everywhere and all the time except at the cutting interface, during the cut—the one place and time where it's wanted. However, a newer form of aerosol delivery, (minimum quantity of lubricant),
avoids both of those problems. The delivery of the aerosol is directly through the flutes of the tool (it arrives directly through or around the
insert Insert may refer to:
*Insert (advertising)
*Insert (composites)
*Insert (effects processing)
*Insert (filmmaking)
*Insert key on a computer keyboard, used to switch between insert mode and overtype mode
*Insert (molecular biology)
*Insert (SQL)
*Fi ...
itself—an ideal type of cutting fluid delivery that traditionally has been unavailable outside of a few contexts such as
gun drill
Gun drills (through coolant drill) are straight fluted drills which allow cutting fluid (either compressed air or a suitable liquid) to be injected through the drill's hollow body to the cutting face. They are used for deep hole drilling—a ...
ing or expensive, state-of-the-art liquid delivery in production milling). MQL's aerosol is delivered in such a precisely targeted way (with respect to both location and timing) that the net effect seems almost like dry machining from the operators' perspective.
The chips generally seem like dry-machined chips, requiring no draining, and the air is so clean that machining cells can be stationed closer to inspection and assembly than before.
MQL doesn't provide much cooling in the sense of heat transfer, but its well-targeted lubricating action prevents some of the heat from being generated in the first place, which helps to explain its success.
CO2 Coolant
Carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
(chemical formula CO
2) is also used as a
coolant
A coolant is a substance, typically liquid, that is used to reduce or regulate the temperature of a system. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, chemically inert and neither causes nor promotes corrosio ...
. In this application pressurized liquid CO
2 is allowed to expand and this is accompanied by a drop in temperature, enough to cause a change of phase into a solid. These solid crystals are redirected into the cut zone by either external nozzles or through-the-spindle delivery, to provide temperature controlled cooling of the cutting tool and work piece.
Air or other gases (e.g., nitrogen)
Ambient air, of course, was the original machining coolant. Compressed air, supplied through pipes and hoses from an
air compressor
An air compressor is a pneumatic device that converts power (using an electric motor, diesel or gasoline engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of several methods, an air compressor forces ...
and discharged from a nozzle aimed at the tool, is sometimes a useful coolant. The force of the decompressing air stream blows chips away, and the decompression itself has a slight degree of cooling action. The net result is that the heat of the machining cut is carried away a bit better than by ambient air alone. Sometimes liquids are added to the air stream to form a mist (mist coolant systems,
described above).
Liquid nitrogen
Liquid nitrogen—LN2—is nitrogen in a liquid state at low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, low viscosity liquid that is wide ...
, supplied in pressurized steel bottles, is sometimes used in similar fashion. In this case, boiling is enough to provide a powerful refrigerating effect. For years this has been done (in limited applications) by flooding the work zone. Since 2005, this mode of coolant has been applied in a manner comparable to
MQL (with through-the-spindle and through-the-tool-tip delivery). This refrigerates the body and tips of the tool to such a degree that it acts as a "thermal sponge", sucking up the heat from the tool–chip interface.
This new type of nitrogen cooling is still under patent. Tool life has been increased by a factor of 10 in the milling of tough metals such as
titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
and
inconel
Inconel is a registered trademark of Special Metals Corporation for a family of austenitic nickel-chromium-based superalloys.
Inconel alloys are oxidation-corrosion-resistant materials well suited for service in extreme environments subjected t ...
.
Alternatively, using airflow combined with a quick evaporating substance (ex. alcohol, water etc.) can be used as an effective coolant when handling hot pieces that cannot be cooled by alternate methods.
Past practice
* In 19th-century machining practice, it was not uncommon to use plain water. This was simply a practical expedient to keep the cutter cool, regardless of whether it provided any lubrication at the cutting edge–chip interface. When one considers that
high-speed steel
High-speed steel (HSS or HS) is a subset of tool steels, commonly used as cutting tool material.
It is often used in power-saw blades and drill bits. It is superior to the older high-carbon steel tools used extensively through the 1940s in that ...
(HSS) had not been developed yet, the need to cool the tool becomes all the more apparent. (HSS retains its hardness at high temperatures; other carbon tool steels do not.) An improvement was soda water (
sodium bicarbonate
Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3−) ...
in water), which better inhibited the rusting of machine slides. These options are generally not used today because more effective alternatives are available.
* Animal fats such as
tallow
Tallow is a rendering (industrial), rendered form of beef or mutton fat, primarily made up of triglycerides.
In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain techn ...
or
lard
Lard is a semi-solid white fat product obtained by rendering the fatty tissue of a pig.[Lard]
entry in the o ...
were very popular in the past. These are used infrequently today, because of the wide variety of other choices, but remain as an option.
* Old machine shop training texts speak of using
red lead
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
and
white lead
White lead is the basic lead carbonate 2PbCO3·Pb(OH)2. It is a complex salt, containing both carbonate and hydroxide ions. White lead occurs naturally as a mineral, in which context it is known as hydrocerussite, a hydrate of cerussite. It was ...
, often mixed into lard or lard oil. This practice is obsolete due to the toxicity of lead.
* From the mid-20th century to the 1990s,
1,1,1-trichloroethane
The organic compound 1,1,1-trichloroethane, also known as methyl chloroform, is a chloroalkane. This colorless, sweet-smelling liquid was once produced industrially in large quantities for use as a solvent. It is regulated by the Montreal Protoco ...
was used as an additive to make some cutting fluids more effective. In shop-floor slang it was referred to as "one-one-one". It has been phased out because of its
ozone-depleting and
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
-depressing properties.
Safety concerns
Cutting fluids present some mechanisms for causing illness or injury in workers.
[NIOSH (2007)]
Health hazard evaluation and technical assistance report: HETA 005-0227-3049
Diamond Chain Company, Indianapolis, Indiana. Occupational exposure is associated with increases in
cardiovascular disease
Cardiovascular disease (CVD) is a class of diseases that involve the heart or blood vessels. CVD includes coronary artery diseases (CAD) such as angina and myocardial infarction (commonly known as a heart attack). Other CVDs include stroke, h ...
.
These mechanisms are based on the external (skin) or internal contact involved in machining work, including touching the parts and tooling; being splattered or splashed by the fluid; or having mist settle on the skin or enter the mouth and nose in the normal course of
breathing
Breathing (or ventilation) is the process of moving air into and from the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxygen.
All aerobic creatures need oxygen for cellular ...
.
The mechanisms include the chemical toxicity or physical irritating ability of:
* the fluid itself
* the metal particles (from previous cutting) that are borne in the fluid
* the
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l or
fungal
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
populations that naturally tend to grow in the fluid over time
* the
biocide
A biocide is defined in the European legislation as a chemical substance or microorganism intended to destroy, deter, render harmless, or exert a controlling effect on any harmful organism. The US Environmental Protection Agency (EPA) uses a slig ...
s that are added to inhibit those life forms
* the
corrosion inhibitor
In chemistry, a corrosion inhibitor or anti-corrosive 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, that comes into contact with the fluid. The effectiveness ...
s that are added to protect the machine and tooling
* the
tramp oils that result from the way oils (the lubricants for the slideways) inevitably finding their way into the coolant
The toxicity or irritating ability is usually not high, but it is sometimes enough to cause problems for the skin or for the tissues of the
respiratory tract
The respiratory tract is the subdivision of the respiratory system involved with the process of respiration in mammals. The respiratory tract is lined with respiratory epithelium as respiratory mucosa.
Air is breathed in through the nose to th ...
or
alimentary tract
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
(e.g., the mouth, larynx, esophagus, trachea, or lungs).
Some of the diagnoses that can result from the mechanisms explained above include
irritant contact dermatitis
Irritant contact dermatitis is a form of contact dermatitis that can be divided into forms caused by chemical irritants and those caused by physical irritants.
Chemical
Chemical irritant contact dermatitis is either acute or chronic, which is u ...
;
allergic contact dermatitis
Allergic contact dermatitis (ACD) is a form of contact dermatitis that is the manifestation of an allergic response caused by contact with a substance; the other type being irritant contact dermatitis (ICD).
Although less common than ICD, ACD is ...
;
occupational acne;
tracheitis
Tracheitis is an inflammation of the trachea.
Although the trachea is usually considered part of the lower respiratory tract, in ICD-10 tracheitis is classified under "acute upper respiratory infections".
Symptoms
* Increasing deep or barking cr ...
;
esophagitis
Esophagitis, also spelled oesophagitis, is a disease characterized by inflammation of the esophagus. The esophagus is a tube composed of a mucosal lining, and longitudinal and circular smooth muscle fibers. It connects the pharynx to the stomach; s ...
;
bronchitis
Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
;
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
;
allergy
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...
;
hypersensitivity pneumonitis
Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis (EAA) is a syndrome caused by the repetitive inhalation of antigens from the environment in susceptible or sensitized people. Common antigens include molds, bacteria, bird dropping ...
(HP); and worsening of pre-existing respiratory problems.
Safer cutting fluid formulations provide a resistance to tramp oils, allowing improved filtration separation without removing the base additive package.
Room ventilation, splash guards on machines, and
personal protective equipment
Personal protective equipment (PPE) is protective clothing, helmets, goggles, or other garments or equipment designed to protect the wearer's body from injury or infection. The hazards addressed by protective equipment include physical, elec ...
(PPE) (such as
safety glasses
Glasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or t ...
,
respirator
A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respir ...
masks, and
gloves
A glove is a garment covering the hand. Gloves usually have separate sheaths or openings for each finger and the thumb.
If there is an opening but no (or a short) covering sheath for each finger they are called fingerless gloves. Fingerless glov ...
) can mitigate hazards related to cutting fluids.
[NIOSH (1998)]
Criteria for a recommended standard: occupational exposure to metalworking fluids
Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. DHHS (NIOSH) Pub. No. 98-102. Additionally, Skimmers may be used to remove tramp oil from the surface of cutting fluid, which prevents the growth of micro-organisms.
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
l growth is predominant in petroleum-based cutting fluids. Tramp oil along with human hair or skin oil are some of the debris during cutting which accumulates and forms a layer on the top of the liquid; anaerobic bacteria proliferate due to a number of factors. An early sign of the need for replacement is the "Monday-morning smell" (due to lack of usage from Friday to Monday).
Antiseptic
An antiseptic (from Greek ἀντί ''anti'', "against" and σηπτικός ''sēptikos'', "putrefactive") is an antimicrobial substance or compound that is applied to living tissue/skin to reduce the possibility of infection, sepsis, or putre ...
s are sometimes added to the fluid to kill bacteria. Such use must be balanced against whether the antiseptics will harm the cutting performance, workers' health, or the environment. Maintaining as low a fluid temperature as practical will slow the growth of microorganisms.
Some health and safety regulators (such as the HSE in the United Kingdom) require weekly testing of metal working fluids to help maintain the fluid's health. These tests involve checking the bacterial CFU/ml Level of the MWF (using
Dipslides) and the pH level by using either a pH meter or pH test strips (since a low pH can be caused by a high bacterial level).
Degradation, replacement, and disposal
Cutting fluids degrade over time due to contaminants entering the lubrication system. A common type of degradation is the formation of ''tramp oil'', also known as ''sump oil'', which is unwanted oil that has mixed with cutting fluid.
[.] It originates as
lubrication
Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.
Lubrication mechanisms such as fluid-lubric ...
oil that seeps out from the
slideways and washes into the coolant mixture, as the protective film with which a steel supplier coats
bar stock
Bar stock, also (colloquially) known as blank, slug or billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products. Bar stock is available in a variety of extrusion shapes and lengths. The most commo ...
to prevent rusting, or as
hydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
oil leaks. In extreme cases it can be seen as a film or skin on the surface of the coolant or as floating drops of oil.
Skimmers are used to separate the tramp oil from the coolant. These are typically slowly rotating vertical discs that are partially submerged below the coolant level in the main reservoir. As the disc rotates the tramp oil clings to each side of the disc to be scraped off by two wipers, before the disc passes back through the coolant. The wipers are in the form of a channel that then redirects the tramp oil to a container where it is collected for disposal. Floating
weir
A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...
skimmers are also used in these situation where temperature or the amount of oil on the water becomes excessive.
Since the introduction of CNC additives, the tramp oil in these systems can be managed more effectively through a continuous separation effect. The tramp oil accumulation separates from the aqueous or oil based coolant and can be easily removed with an absorbent.
Old, used cutting fluid must be disposed of when it is fetid or chemically degraded and has lost its usefulness. As with used motor oil or other wastes, its impact on the environment should be mitigated. Legislation and regulation specify how this mitigation should be achieved. Modern cutting fluid disposal involves techniques such as
ultrafiltration
Ultrafiltration (UF) is a variety of membrane filtration in which forces such as pressure or concentration gradients lead to a separation through a semipermeable membrane. Suspended solids and solutes of high molecular weight are retained in the s ...
using polymeric or ceramic membranes which concentrates the suspended and emulsified oil phase.
Chip Chromatin immunoprecipitation (ChIP) is a type of immunoprecipitation experimental technique used to investigate the interaction between proteins and DNA in the cell. It aims to determine whether specific proteins are associated with specific genom ...
handling and coolant management are interrelated. Over the decades they have been improved, to the point that many metalworking operations now use engineered solutions for the overall cycle of collecting, separating, and recycling both chips and coolant. For example, the chips are graded by size and type, tramp metals (such as bolts and scrap parts) are separated out, the coolant is centrifuged off the chips (which are then dried for further handling), and so on.
References
Notes
Bibliography
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External links
Metalworking Fluids - NIOSH Workplace Safety and Health Topic- National Institute for Occupational Safety and Health
{{DEFAULTSORT:Cutting Fluid
Coolants
Metalworking
Lubricants
Petroleum products
Oils
it:Lubrorefrigerante