Introduction to Grinding Fluids 261
Introduction to Grinding Fluids provides an overview of the uses, types, and selection considerations of grinding fluids, or coolants, used in various machining operations. Appropriate grinding fluid use depends on the type of operation, machine tool, and combination of tool and workpiece materials. The basic types of grinding fluids include various combinations of oils, water, chemicals, and additives, and are classified by their contents. The class describes each category of fluid, its optimal uses, benefits, and drawbacks, as well as ideal delivery methods, maintenance, and basic fluid safety and disposal.
Selecting, using, and maintaining the appropriate grinding fluid is a key factor in the success of a grinding operation. Proper coolant application can optimize wheel performance and improve finished parts, reducing scrap and tool cost. Additionally, awareness of grinding fluid hazards and maintenance can increase workplace safety and reduce coolant costs.
Number of Lessons 18
- Grinding Fluid
- Friction and Heat
- Grinding Fluid Safety
- Grinding Fluid Basics
- Straight Oils
- Soluble Oils
- Synthetic Fluids
- Types of Grinding Fluid Review
- How to Select a Grinding Fluid
- Fluid Delivery Methods
- Reviewing Coolant Considerations
- Grinding Fluid Concentrate
- Water Quality
- Grinding Fluid Contaminants
- Cleaning Grinding Fluids
- Grinding Fluid Disposal
- Dry Grinding
- Final Review
- List the functions of grinding fluid.
- Describe the relationship between friction and heat in grinding.
- Describe the necessary safety precautions for working with grinding fluids.
- Describe straight oils.
- Describe soluble oils.
- Describe synthetic fluids. Describe semi-synthetic fluids.
- Describe the considerations for selecting a grinding fluid.
- Describe the methods of grinding fluid delivery.
- Describe the appropriate levels of grinding fluid concentrate.
- Describe water quality considerations.
- Describe how grinding fluid can become contaminated.
- List the methods of cleaning grinding fluids.
- Describe grinding fluid disposal.
- Describe dry grinding.
The state of having a pH value below 7. Acidity is the opposite of alkalinity.
A cutting or grinding oil that releases lubricating sulfur during machining. Active grinding oils include sulfurized and sulfochlorinated mineral oils.
Any substance added to a grinding fluid to improve lubrication, cooling, or both during a grinding process. Additives in grinding fluid include chlorine, sulfur, and phosphorus.
Requiring oxygen to exist. Aerobic bacteria multiply rapidly in grinding fluid that is agitated, such as during a grinding operation.
The state of having a pH value above 7. Alkalinity is the opposite of acidity.
A nonferrous, silvery-white metal that is soft and light. Aluminum often requires the use of a super-fatted oil for grinding.
Not requiring oxygen to exist. Anaerobic bacteria multiply in grinding fluid that has been sitting unused.
A fatty oil derived from tissues from livestock such as cows, pigs, or sheep. Animal oils are a type of inactive straight oil.
A long garment designed to protect the wearer from splashing fluid or other dangerous substances. An apron is an essential piece of PPE when working with a grinding machine that is not enclosed.
arc of cut
The area where the grinding wheel contacts the workpiece. The arc of cut is where material is removed and frictional heat is generated during the grinding operation.
A biological contaminant that can develop in grinding fluid. Bacteria greatly increase the risk associated with handling or breathing grinding fluid.
Substances designed to kill living cells. Biocides are added to cutting or grinding fluids to prevent biological or fungal contamination.
A naturally occurring earth metal, particles of which are often found in tap water. Calcium contributes to water hardness.
The formation of malignant cells that surround and invade healthy tissue. Cancer is a potentially fatal illness associated with overexposure to certain grinding fluids.
central fluid system
A system designed to deliver fluid to multiple grinders. Central fluid systems may include a fluid-cleaning device such as a vacuum filter unit or a skimmer.
A force which keeps an object moving in a circular or curved path. Centripetal force can be exerted by a centrifuge.
A device that uses centrifugal acceleration to separate out denser material or debris from a grinding fluid. Centrifuges are used to clean grinding fluid when there is minimal swarf.
Grinding fluids that consist of synthetic materials mixed in water. Chemical fluids are more commonly called synthetic fluids.
Small pieces of unwanted material removed by the grinding process. Chips should be washed out of the arc of cut using grinding fluid.
A naturally occurring element with a wide range of applications. Chlorine is used as an additive to increase lubrication properties.
A chemical mixture that is designed to be mixed with water before use. Water-miscible grinding fluids are sold as concentrates.
A red itchy rash caused by skin contact with a substance. Contact dermatitis can be caused by skin contact with grinding fluid.
To deteriorate the useful properties in a material due to oxidation. Corrosion in grinding machines can be caused by water.
creep feed grinding
A grinding process that cuts deeply into the workpiece. Creep feed grinding is useful for removing large amounts of material quickly.
An additive used in cutting or grinding fluids to help prevent the development of foam and bubbles. Defoamers improve the cooling ability of the fluid.
Grinding operations that use no grinding fluids. Dry grinding may utilize solid lubricants and cooling gases.
A material's ability to be drawn, stretched, or formed without breaking. Ductility is generally present in the absence of strength.
A substance that allows small droplets of one liquid to be suspended in another liquid. Emulsifiers allow water-miscible fluids to mix evenly.
Equipment designed to clean or control the environment surrounding a grinding operation. Environmental controls can include filtration systems, ventilation systems, or other cleaning devices.
Environmental Protection Agency
EPA. The U.S. federal government agency that carries on research, monitoring, standard-setting, and enforcement activities to ensure a clean, healthy environment. The Environmental Protection Agency maintains standards for any fluids that contain potentially harmful ingredients.
Environmental Protection Agency. The U.S. federal government agency that carries on federal research, monitoring, standard-setting, and enforcement activities to ensure a clean, healthy environment. The EPA maintains standards for any fluids that contain potentially harmful ingredients.
The vaporization of water into the surrounding air. Evaporation increases the concentration of water-miscible grinding fluids.
extreme-pressure soluble oils
EP soluble oils. A soluble oil that contains additives to increase lubrication under extreme cutting or grinding conditions. Extreme-pressure soluble oils often contain additives such as sulfur or chlorine to increase lubrication.
A naturally occurring inactive oil that has excellent lubricating properties. Fatty oils include animal, vegetable, and marine oils.
A metal that contains iron. Steel is a ferrous metal.
A final grinding pass that emphasizes tight tolerances and smooth surface finish. Finishing cuts require fluids with excellent lubrication.
flood fluid application
A method of grinding fluid application that delivers a large amount of fluid, flooding the work area. In flood fluid application, grinding fluid is delivered through nozzles and completely covers the workpiece and the grinding wheel.
The action of frothy bubbles being formed. Foaming should be avoided, as it can introduce air into grinding fluid.
A force that resists motion between two components that are in contact with each other. Friction produces heat.
Grinding fluids that consist of synthetic materials mixed in water. Full-synthetic fluids are sometimes called chemical fluids.
A biological contaminant that can grow in grinding fluid. Fungus greatly increases the risk of handling or breathing grinding fluid.
The unwanted formation of a smooth surface on a grinding wheel. Glazing occurs when the abrasive grains of the wheel become worn.
Thin, disposable gloves made from latex or another chemically resistant material. Gloves help to protect the operator from contact with grinding fluid.
A type of tight-fitting eye protection that completely covers the eyes, the sockets, and the surrounding facial area. Goggles offer protection from impact, dust, chips, and splashes.
A soft, black form of carbon that can be used as a lubricant. Graphite is usually sold as a solid or powder.
A substance, usually liquid, used to lubricate or to reduce the temperature of a part being ground. Grinding fluid is sometimes informally referred to as coolant.
grinding fluid sump
The tank on a machine tool that holds cutting or grinding fluid. The grinding fluid sump should be checked regularly to ensure the cleanliness and proper water/concentrate ratio of the grinding fluid.
A method of grinding fluid application that delivers fluid precisely and at high velocity to the cutting zone. High-pressure delivery is typically more effective than flood cooling, but it may require more expensive machinery.
A liquid that is used to generate power in a hydraulic system. Hydraulic fluid can contaminate grinding fluid.
A cutting or grinding oil that releases very little lubricating sulfur during machining. Inactive oils include mineral oil and fatty oil.
A film that develops between the grinding wheel and the workpiece when grinding fluids with extreme-pressure additives are used. The lubricating film forms when an extreme-pressure additive reacts with metal.
The application of a substance to reduce friction between two surfaces. Lubrication for grinding is provided by grinding fluid.
A physical barrier used to totally contain a grinding operation. A machine enclosure limits operator exposure to grinding fluids.
machine fluid filter
A system designed to filter out swarf and other solid contaminants from grinding fluid. A machine fluid filter system can help to extend the life of the grinding fluid and provide a cleaner and less dangerous environment for the operator.
A naturally occurring earth metal, particles of which are often found in tap water. Magnesium contributes to water hardness.
A device that uses magnetism to capture ferrous debris and remove it from cutting or grinding fluid. Magnetic cleaners are used to clean grinding fluid.
The additional grinding fluid concentrate, water, or both needed to maintain the correct fluid concentration. Make-up rate determines the frequency with which the ratio of concentrate to water must be adjusted.
A fatty oil derived from the tissues of fish, whales, or other marine animals. Marine oils are a type of inactive straight oil.
Material Safety Data Sheet
MSDS. A form that may accompany a chemical in the workplace if an SDS is not provided. Material Safety Data Sheets detail the risks, precautions, and first aid procedures associated with a chemical.
A naturally occurring inactive oil derived from petroleum. Mineral oil is used as both a lubricant and coolant.
mist control system
Any of a number of different systems or devices designed to remove mist or other contaminants related to the grinding process from the air. Mist control systems help to reduce the health risks associated with grinding fluid.
A mineral compound that is used as a solid lubricant. Molybdenum disulfide is similar in appearance to graphite.
A chemical additive used in synthetic fluids for rust prevention. Nitrites are often salts.
A colorless, odorless, naturally occurring gas. Nitrogen can be used for cooling dry grinding operations.
A metal that does not contain iron. Aluminum, copper, and zinc are nonferrous metals.
Occupational Safety and Health Administration
OSHA. A federal government agency dedicated to reducing injuries, illnesses, and deaths in the workplace. The Occupational Safety and Health Administration provides guidelines for handling dangerous substances.
paper gravity filter
A moving paper filter. Paper gravity filters help to clean swarf and other solid contaminants from grinding fluid.
parts per million
PPM. A measurement of the ratio of one substance to another. One part per million means a ratio of one to one million.
personal protective equipment
PPE. Any clothing or device worn to minimize exposure to hazards and prevent injury. In grinding, common personal protective equipment protects hands, arms, and eyes.
A measure of the acidity or alkalinity of a substance. A pH value below 7 is acidic; a pH value above 7 is alkaline.
An instrument used to measure acidity or alkalinity. pH meters typically work by measuring voltage between two electrodes as the meter is dipped into the substance to be measured.
pH testing strips
Small, inexpensive testing devices used to check pH levels in liquid. pH strips change color according to the pH of the substance to which they are exposed.
A mineral sometimes added to grinding fluid. Phosphorus helps to provide additional lubrication.
A grinding action where the grains dig into the workpiece and force material out to the side. Plowing occurs when the removal rate is too low, the grains are not sharp enough, or the grains are poorly angled against the workpiece.
A group of molecules that are linked to each other in a chain-like structure. Polymers can provide lubrication to grinding operations.
A machine designed to move grinding fluid to the grinding area. Pumps used for high-pressure delivery are generally more powerful than pumps used for flood fluid application.
An optical instrument used to measure the concentration of a water-miscible fluid. Refractometers are used to ensure a proper concentrate-to-water ratio in grinding fluid.
A breathing device worn to prevent inhalation of hazardous substances. A respirator filters out chemicals as well as particulate matter.
Of or having to do with breathing and the lungs. Respiratory problems typically affect the lungs, nose, or throat.
An initial grinding operation that removes stock without regard to surface finish. Rough grinding generally requires a grinding fluid with excellent cooling properties.
An initial grinding operation that removes stock without regard to surface finish. Roughing generally requires a grinding fluid with excellent cooling properties.
An elastic material made from the sap of the rubber tree. Rubber can be used as a bond in grinding wheels.
A grinding action where grains slide over the surface of the workpiece without penetrating. Rubbing occurs when the wheel's abrasive grains are not sharp enough or the wheel has become loaded with material.
Safety Data Sheet
SDS. A form that must accompany almost every chemical in the workplace. Safety Data Sheets detail the risks, precautions, and first aid procedures associated with a chemical.
Visible calcium or magnesium buildup. Scale is an indication of very hard water.
Safety data sheet. A form that must accompany almost every chemical in the workplace. SDSs detail the risks, precautions, and first aid procedures associated with a chemical.
A grinding fluid containing a mixture of chemicals, water, and soluble oil. Semi-synthetic fluids are also called semi-chemical fluids.
A resinous substance produced by a particular beetle. Shellac can be used as a bond in grinding wheels.
A device that uses a rotating disk or belt to remove unwanted materials from the surface of cutting or grinding fluid. Skimmers can be used to remove tramp oil.
Materials that can be added to the wheel or workpiece surface to reduce friction. Solid lubricants include graphite and wax.
Grinding fluid that is composed of lubricant-based oil, emulsifiers, and other additives. Soluble oil is made by mixing water with these ingredients in concentrate form in a ratio ranging from 2% to 15% concentrate.
A mixture of multiple liquids and solids in which all components are evenly combined into one substance. Most synthetic grinding fluids are solutions composed of multiple chemicals.
A grinding fluid that is composed of oil and contains no water. Straight oils provide excellent lubrication but do not cool as well as grinding fluids that include water.
sulferized mineral oil
Mineral oil with added sulfur. Sulfurized mineral oil provides additional lubrication beyond the capability of inactive straight oil.
sulfochlorinated mineral oil
Mineral oil with added sulfur and chloride. Sulfochlorinated mineral oil provides additional lubrication beyond the capability of inactive straight oil.
A natural or artificial element with a wide variety of industrial applications. Sulfur can be used as an additive to increase lubrication under severe grinding operations and is particularly advantageous when a high degree of surface finish is required.
super-fatted soluble oils
A grinding fluid with added marine, animal, or vegetable fats. Super-fatted soluble oils provide excellent lubrication.
The tendency of a liquid to minimize its surface area by clinging to itself. Liquids with high surface tension will form into compact droplets when spreading over a surface.
Substances that reduce the surface tension of a liquid. Surface-active agents are also called surfactants.
surface-active grinding fluids
A grinding fluid that contains surfactants. Surface-active grinding fluids can provide improved lubrication.
Substances that reduce the surface tension of a liquid. Surfactants are also called surface-active agents.
A fluid mixture in which small particles of multiple liquids are dispersed evenly. Many grinding fluids are made of oils suspended in water.
The gritty combination of chips, abrasive grains, and worn bonding material that is produced during grinding. Swarf can clog a grinding wheel and cause it to function improperly.
A piece of material used to check the pH of grinding fluid. Test strips are cheap and easily obtained.
An acceptable deviation from a desired dimension that still meets specifications. Tolerances indicate the allowable difference between a physical feature and its intended design.
Hydraulic oil or grease from the machine that has contaminated the grinding fluid. Tramp oil is usually a result of machine lubrication systems and leaks.
vacuum filter units
A device commonly used to filter contaminants from grinding fluid. Vacuum filter units pull grinding fluid through a rolled fabric filter.
A fatty oil derived from plant byproducts such as castor oil and coconut oil. Vegetable oils are a type of inactive straight oil.
A means of cleaning and recirculating air. Ventilation systems are necessary in certain grinding fluid operations, particularly high-volume production, to prevent inhalation of grinding fluid.
A measure of the mineral content of water. Hard water is generally unsuitable for use in grinding fluid.
Liquids that can thoroughly mix with water. Water-miscible coolants contain oil or polymers, water, and additives.
A pliable compound that can be used as a lubricant for grinding. Wax used for grinding is typically beeswax or paraffin.
EP additives. A grinding fluid additive that helps create a film in order to increase lubrication during a grinding operation. Sulfur is an example of an extreme-pressure additive.
EP additives. Additives that help create a film in the arc of cut that provides additional lubrication under high pressures and temperatures. Extreme-pressure additives include chlorine, sulfur, and phosphorus.