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An abrasive is a material, often a
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of ...
. While finishing a material often means
polishing Polishing is the process of creating a smooth and shiny surface by rubbing it or by applying a chemical treatment, leaving a clean surface with a significant specular reflection (still limited by the index of refraction of the material accordin ...
it to gain a smooth, reflective surface, the process can also involve roughening as in satin, matte or beaded finishes. In short, the ceramics which are used to cut, grind and polish other softer materials are known as abrasives. Abrasives are extremely commonplace and are used very extensively in a wide variety of industrial, domestic, and technological applications. This gives rise to a large variation in the physical and chemical composition of abrasives as well as the shape of the abrasive. Some common uses for abrasives include grinding, polishing, buffing, honing,
cutting Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force. Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
,
drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at ...
, sharpening,
lapping Lapping is a machining process in which two surfaces are rubbed together with an abrasive between them, by hand movement or using a machine. Lapping often follows other subtractive processes with more aggressive material removal as a first ste ...
, and
sanding upright=1.35, Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)). Sandpaper and glasspaper are names used for a type of coated abrasive that consists of sheets of paper or cloth with abrasive material glued to ...
(see abrasive machining). (For simplicity, "mineral" in this article will be used loosely to refer to both minerals and mineral-like substances whether man-made or not.) Files are not abrasives; they remove material not by scratching or rubbing, but by the cutting action of sharp teeth which have been cut into the surface of the file, very much like those of a saw. However, diamond files are a form of coated abrasive (as they are metal rods coated with diamond powder).


Mechanics of abrasion

Abrasives generally rely upon a difference in hardness between the abrasive and the material being worked upon, the abrasive being the harder of the two substances. However, is not necessary as any two solid materials that repeatedly rub against each other will tend to wear each other away; examples include, softer shoe soles wearing away wooden or stone steps over decades or centuries or
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...
s abrading stone valleys. Typically, materials used as abrasives are either hard
minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed ...
(rated at 7 or above on
Mohs scale of mineral hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by t ...
) or are synthetic stones, some of which may be chemically and physically identical to naturally occurring minerals but which cannot be called minerals as they did not arise naturally. (While useful for comparative purposes, the Mohs scale is of limited value to materials engineers as it is an arbitrary, ordinal, irregular scale.)
Diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...
, a common abrasive, for instance occurs both naturally and is industrially produced, as is
corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pr ...
which occurs naturally but which is nowadays more commonly manufactured from
bauxite Bauxite is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)) and diaspore (α-AlO ...
. However, even softer minerals like calcium carbonate are used as abrasives, such as "polishing agents" in toothpaste. These minerals are either crushed or are already of a sufficiently small size (anywhere from macroscopic grains as large as about 2 mm to microscopic grains about 0.001 mm in diameter) to permit their use as an abrasive. These grains, commonly called grit, have rough edges, often terminating in points which will decrease the surface area in contact and increase the localised contact
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
. The abrasive and the material to be worked are brought into contact while in relative motion to each other. Force applied through the grains causes fragments of the worked material to break away, while simultaneously smoothing the abrasive grain and/or causing the grain to work loose from the rest of the abrasive. Some factors which will affect how quickly a substance is abraded include: *Difference in hardness between the two substances: a much harder abrasive will cut faster and deeper *Grain size (grit size): larger grains will cut faster as they also cut deeper *Adhesion between grains, between grains and backing, between grains and matrix: determines how quickly grains are lost from the abrasive and how soon fresh grains, if present, are exposed *Contact force: more force will cause faster abrasion *Loading: worn abrasive and cast off work material tends to fill spaces between abrasive grains so reducing cutting efficiency while increasing friction *Use of lubricant/coolant/metalworking fluid: Can carry away
swarf Swarf, also known as chips or by other process-specific names (such as turnings, filings, or shavings), are pieces of metal, wood, or plastic that are the debris or waste resulting from machining, woodworking, or similar subtractive (material-r ...
(preventing loading), transport heat (which may affect the physical properties of the workpiece or the abrasive), decrease friction (with the substrate or matrix), suspend worn work material and abrasives allowing for a finer finish, conduct stress to the workpiece.


Abrasive minerals

Abrasives may be classified as either natural or synthetic. When discussing
sharpening stone Sharpening stones, or whetstones, are used to sharpen the edges of steel tools such as knives through grinding and honing. Such stones come in a wide range of shapes, sizes, and material compositions. They may be flat, for working flat edg ...
s, natural stones have long been considered superior but advances in material technology are seeing this distinction become less distinct. Many synthetic abrasives are effectively identical to a natural mineral, differing only in that the synthetic mineral has been manufactured rather than mined. Impurities in the natural mineral may make it less effective. Some naturally occurring abrasives are: *
Calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratc ...
(calcium carbonate) * Emery (impure corundum) * Diamond dust (synthetic diamonds are used extensively) *
Novaculite Novaculite, also called Arkansas Stone, is a microcrystalline to cryptocrystalline rock type that consists of silica in the form of chert or flint. It is commonly white to grey or black in color, with a specific gravity that ranges from 2.2 to 2.5 ...
*
Pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...
*
Iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally a ...
*
Sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class ...
*
Corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium and chromium. It is a rock-forming mineral. It is a naturally transparent material, but can have different colors depending on the pr ...
*
Garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...
*
Sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicat ...
*
Rotten stone Rotten stone, sometimes spelled as rottenstone, also known as tripoli, is fine powdered porous rock used as a polishing abrasive for metalsmithing and in woodworking. It is usually weathered limestone mixed with diatomaceous, amorphous, or cryst ...
(Tripoli) * Powdered
feldspar Feldspars are a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagioclase'' (sodium-calcium) felds ...
*
Staurolite Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and the chemical formula: Fe2+2Al9O6(SiO4)4(O,OH)2. Magnesium, ...
Some abrasive minerals (such as
zirconia alumina Zirconia alumina is commonly used as a sand-blasting medium. It is typically used as an abrasive in casting and foundry processes. Zirconia alumina is a mixture of zirconium dioxide Zirconium dioxide (), sometimes known as zirconia (not to be co ...
) occur naturally but are sufficiently rare or sufficiently more difficult or costly to obtain such that a synthetic stone is used industrially. These and other artificial abrasives include: *
Borazon Borazon is a brand name of a cubic form of boron nitride (cBN). Its color ranges from black to brown and gold, depending on the chemical bond. It is one of the hardest known materials, along with various forms of diamond and kinds of boron nitride ...
(cubic
boron nitride Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagonal ...
or CBN) *
Ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, ...
* Ceramic aluminium oxide * Ceramic iron oxide * Corundum (alumina or aluminium oxide) *
Dry ice Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
*
Glass Glass is a non- crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenchin ...
powder *
Steel abrasive Steel abrasives are steel particles that are used as abrasive or peening media. They are usually available in two different shapes (shot and grit) that address different industrial applications. Steel shot refers to spherical grains made of molt ...
*
Silicon carbide Silicon carbide (SiC), also known as carborundum (), is a hard chemical compound containing silicon and carbon. A semiconductor, it occurs in nature as the extremely rare mineral moissanite, but has been mass-produced as a powder and crystal s ...
(carborundum) * Zirconia alumina *
Boron carbide Boron carbide (chemical formula approximately B4C) is an extremely hard boron– carbon ceramic, a covalent material used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. With a Vickers ...
*
Slag Slag is a by-product of smelting ( pyrometallurgical) ores and used metals. Broadly, it can be classified as ferrous (by-products of processing iron and steel), ferroalloy (by-product of ferroalloy production) or non-ferrous/base metals (by-p ...
s


Manufactured abrasives

Abrasives are shaped for various purposes. Natural abrasives are often sold as dressed stones, usually in the form of a rectangular block. Both natural and synthetic abrasives are commonly available in a wide variety of shapes, often coming as bonded or coated abrasives, including blocks, belts, discs, wheels, sheets, rods and loose grains.


Bonded abrasives

A bonded abrasive is composed of an abrasive material contained within a
matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...
, although very fine aluminium oxide abrasive may comprise
sintered Clinker nodules produced by sintering Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction. Sintering happens as part of a manufacturing ...
material. This matrix is called a binder and is often a
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay pa ...
, a
resin In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on nat ...
, a glass or a
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
. This mixture of binder and abrasive is typically shaped into blocks, sticks, or wheels. The most common abrasive used is aluminium oxide. Also common are silicon carbide,
tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
and
garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...
. Artificial sharpening stones are often a bonded abrasive and are readily available as a two sided block, each side being a different grade of grit. Grinding wheels are cylinders that are rotated at high speed. While once worked with a foot pedal or hand crank, the introduction of electric motors has made it necessary to construct the wheel to withstand greater radial stress to prevent the wheel flying apart as it spins. Similar issues arise with cutting wheels, which are often structurally reinforced with impregnated fibres. High relative speed between abrasive and workpiece often makes necessary the use of a lubricant of some kind. Traditionally, they were called
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 corrosi ...
s as they were used to prevent frictional heat build up which could damage the workpiece (such as ruining the temper of a blade). Some research suggests that the heat transport property of a lubricant is less important when dealing with metals as the metal will quickly conduct heat from the work surface. More important are their effects upon lessening tensile stresses while increasing some compressive stresses and reducing "thermal and mechanical stresses during chip formation". Various shapes are also used as heads on
rotary tool Die grinders and rotary tools are handheld power tools used for grinding, sanding, honing, polishing, or machining material (typically metal, but also plastic or wood). All such tools are conceptually similar, with no bright dividing line ...
s used in precision work, such as
scale model A scale model is a physical model which is geometrically similar to an object (known as the prototype). Scale models are generally smaller than large prototypes such as vehicles, buildings, or people; but may be larger than small prototypes ...
ling. Bonded abrasives need to be trued and dressed after they are used. Dressing is the cleaning of the waste material (swarf and loose abrasive) from the surface and exposing fresh grit. Depending upon the abrasive and how it was used, dressing may involve the abrasive being simply placed under running water and brushed with a stiff brush for a soft stone or the abrasive being ground against another abrasive, such as aluminium oxide used to dress a grinding wheel. Truing is restoring the abrasive to its original surface shape. Wheels and stones tend to wear unevenly, leaving the cutting surface no longer flat (said to be "dished out" if it is meant to be a flat stone) or no longer the same diameter across the cutting face. This will lead to uneven abrasion and other difficulties.


Coated abrasives

A ''coated abrasive'' comprises an abrasive fixed to a backing material such as
paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distribu ...
,
cloth Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, different fabric types, etc. At first, the word "textiles" only referred to woven fabrics. However, weaving is not the ...
, rubber, resin,
polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natura ...
or even
metal A metal (from ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, e ...
, many of which are flexible.
Sandpaper upright=1.35, Sheets of sandpaper with different grit sizes (40 (coarse), 80, 150, 240, 600 (fine)). Sandpaper and glasspaper are names used for a type of coated abrasive that consists of sheets of paper or cloth with abrasive material glued to ...
is a very common coated abrasive. Coated abrasives are most commonly the same minerals as are used for bonded abrasives. A bonding agent (often some sort of adhesive or resin) is applied to the backing to provide a flat surface to which the grit is then subsequently adhered. A woven backing may also use a filler agent (again, often a resin) to provide additional resilience. Coated abrasives may be shaped for use in rotary and orbital sanders, for wrapping around sanding blocks, as handpads, as closed loops for use on belt grinders, as striking surfaces on
match A match is a tool for starting a fire. Typically, matches are made of small wooden sticks or stiff paper. One end is coated with a material that can be ignited by friction generated by striking the match against a suitable surface. Wooden mat ...
boxes, on
diamond plate Tread plate, also known as checker plate and diamond plate, is a type of metal stock with a regular pattern or lines on one side for slip resistance. The most common alloy used for aluminum tread plate is 6061, although 5086-H34 and 3003-H231 are ...
s and diamond steels. Diamond tools, though for cutting, are often abrasive in nature.


Other abrasives and their uses

Sand, glass beads, metal pellets
copper slag Copper slag is a by-product of copper extraction by smelting. During smelting, impurities become slag which floats on the molten metal. Slag that is quenched in water produces angular granules which are disposed of as waste or utilized as discusse ...
and dry ice may all be used for a process called
sandblasting Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove s ...
(or similar, such as the use of glass beads which is "bead blasting"). Dry ice will sublimate leaving behind no residual abrasive. Cutting compound used on automotive paint is an example of an abrasive suspended in a liquid, paste or wax, as are some polishing liquids for
silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...
ware and optical media. The liquid, paste or wax acts as a binding agent that keeps the abrasive attached to the cloth which is used as a backing to move the abrasive across the work piece. On cars in particular, wax may serve as both a protective agent by preventing exposure of the paint of metal to air and also act as an optical filler to make scratches less noticeable.
Toothpaste Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, ...
contains calcium carbonate or
silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
as a "polishing agent" to remove plaque and other matter from teeth as the hardness of calcium carbonate is less than that of
tooth enamel Tooth enamel is one of the four major tissues that make up the tooth in humans and many other animals, including some species of fish. It makes up the normally visible part of the tooth, covering the crown. The other major tissues are dentin, ...
but more than that of the contaminating agent. Very fine rouge powder was commonly used for grinding glass, being somewhat replaced by modern ceramics, and is still used in jewellery making for a highly reflective finish. Cleaning products may also contain abrasives suspended in a paste or cream. They are chosen to be reasonably safe on some
linoleum Linoleum, sometimes shortened to lino, is a floor covering made from materials such as solidified linseed oil (linoxyn), pine resin, ground cork dust, sawdust, and mineral fillers such as calcium carbonate, most commonly on a burlap or canva ...
,
tile Tiles are usually thin, square or rectangular coverings manufactured from hard-wearing material such as ceramic, stone, metal, baked clay, or even glass. They are generally fixed in place in an array to cover roofs, floors, walls, edges, or ...
, metal or stone surfaces. However, many
laminate Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing materia ...
surfaces and ceramic topped stoves are easily damaged by these abrasive compounds. Even ceramic/pottery tableware or cookware can damage these surfaces, particularly the bottom of the tableware, which is often unglazed in part or in whole and acts as simply another bonded abrasive. Metal pots and stoves are often scoured with abrasive cleaners, typically in the form of the aforementioned cream or paste or of
steel wool Steel wool, also known as iron wool, wire wool or wire sponge, is a bundle of very fine and flexible sharp-edged steel filaments. It was described as a new product in 1896.''Iron Age'', Vol. LVII, p.871, cited by ''Journal of the Iron and Steel ...
and non woven
scouring pad A scouring pad or scourer is a small pad of metal or plastic mesh used for scouring a surface. Some scouring pads have one side made of a soft sponge-like material and the other is the aforementioned mesh. History The scouring pad has been re ...
s which holds fine grits abrasives. Human skin is also subjected to abrasion in the form of exfoliation. Abrasives for this can be much softer and more exotic than for other purposes and may include things like
almond The almond (''Prunus amygdalus'', syn. ''Prunus dulcis'') is a species of tree native to Iran and surrounding countries, including the Levant. The almond is also the name of the edible and widely cultivated seed of this tree. Within the genu ...
and
oatmeal Oatmeal is a preparation of oats that have been de-husked, steamed, and flattened, or a coarse flour of hulled oat grains (groats) that have either been milled (ground) or steel-cut. Ground oats are also called white oats. Steel-cut oats a ...
.
Dermabrasion Dermabrasion is a type of surgical skin planing, generally with the goal of removing acne, scarring and other skin or tissue irregularities, typically performed in a professional medical setting by a dermatologist or plastic surgeon trained speci ...
and
microdermabrasion Dermabrasion is a type of surgical skin planing, generally with the goal of removing acne, scarring and other skin or tissue irregularities, typically performed in a professional medical setting by a dermatologist or plastic surgeon trained speci ...
are now rather commonplace cosmetic procedures which use mineral abrasives. Scratched compact discs and DVDs may sometimes be repaired through buffing with a very fine compound, the principle being that a multitude of small scratches will be more optically transparent than a single large scratch. However, this does take some skill and will eventually cause the protective coating of the disc to be entirely eroded (especially if the original scratch is deep), at which time, the data surface will be destroyed if abrasion continues.


Choice of abrasive

The shape, size and nature of the workpiece and the desired finish will influence the choice of the abrasive used. A bonded abrasive grind wheel may be used to commercially sharpen a knife (producing a hollow grind), but an individual may then sharpen the same knife with a natural sharpening stone or an even flexible coated abrasive (like a sandpaper) stuck to a soft, non-slip surface to make achieving a convex grind easier. Similarly, a brass mirror may be cut with a bonded abrasive, have its surface flattened with a coated abrasive to achieve a basic shape, and then have finer grades of abrasive successively applied culminating in a wax paste impregnated with rouge to leave a sort of "grainless finish" called, in this case, a "mirror finish". Also, different shapes of adhesive may make it harder to abrade certain areas of the workpiece. Health hazards can arise from any dust produced (which may be ameliorated through the use of a lubricant) which could lead to
silicosis Silicosis is a form of occupational lung disease caused by inhalation of crystalline silica dust. It is marked by inflammation and scarring in the form of nodular lesions in the upper lobes of the lungs. It is a type of pneumoconiosis. Silic ...
(when the abrasive or workpiece is a
silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is a ...
) and the choice of any lubricant. Besides water, oils are the most common lubricants. These may present inhalation hazards, contact hazards and, as friction necessarily produces heat, flammable material hazards. An abrasive which is too hard or too coarse can remove too much material or leave undesired scratch marks. Besides being unsightly, scratching can have other, more serious effects. Excessive abrasion or the presence of scratches may: *diminish or destroy usefulness (as in the case of scratching
optical lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements ...
es and
compact disc The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in O ...
s or dulling
knives A knife ( : knives; from Old Norse 'knife, dirk') is a tool or weapon with a cutting edge or blade, usually attached to a handle or hilt. One of the earliest tools used by humanity, knives appeared at least 2.5 million years ago, as evidenced ...
); *trap dirt, water, or other material; *increase surface area (permitting greater
chemical reactivity In chemistry, reactivity is the impulse for which a chemical substance undergoes a chemical reaction, either by itself or with other materials, with an overall release of energy. ''Reactivity'' refers to: * the chemical reactions of a single su ...
such as increased
rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...
ing which is also affected by matter caught in scratches); *erode or penetrate a coating (such as a paint or a chemical or wear resistant coating); *overly quickly cause an object to wear away (such as a blade or a gemstone); *increase friction (as in jeweled bearings and
piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-t ...
s). A finer or softer abrasive will tend to leave much finer scratch marks which may even be invisible to the naked eye (a "grainless finish"); a softer abrasive may not even significantly abrade a certain object. A softer or finer abrasive will take longer to cut, as it tends to cut less deeply than a coarser, harder material. Also, the softer abrasive may become less effective more quickly as the abrasive is itself abraded. This allows fine abrasives to be used in the polishing of metal and lenses where the series of increasingly fine scratches tends to take on a much more shiny or reflective appearance or greater transparency. Very fine abrasives may be used to coat the
strop A razor strop or simply a strop (sometimes called a razor strap or strap) is a flexible strip of leather, canvas, denim fabric, balsa wood, or other soft material, used to straighten and polish the blade of a straight razor, a knife, or a wood ...
for a cut-throat
razor A razor is a bladed tool primarily used in the removal of body hair through the act of shaving. Kinds of razors include straight razors, safety razors, disposable razors, and electric razors. While the razor has been in existence since bef ...
s, however, the purpose of stropping is not to abrade material but to straighten the burr on an edge. The final stage of sharpening
Japanese sword A is one of several types of traditionally made swords from Japan. Bronze swords were made as early as the Yayoi period (1000 BC – 300 AD), though most people generally refer to the curved blades made from the Heian period (794 – 1185) to t ...
s is called polishing and may be a form of superfinishing. Different chemical or structural modifications may be made to alter the cutting properties of the abrasive. Other very important considerations are price and availability. Diamond, for a long time considered the hardest substance in existence, is actually softer than fullerite and even harder aggregated diamond nanorods, both of which have been synthesised in laboratories, but no commercial process has yet been developed. Diamond itself is expensive due to scarcity in nature and the cost of synthesising it. Bauxite is a very common ore which, along with corundum's reasonably high hardness, contributes to corundum's status as a common, inexpensive abrasive. Thought must be given to the desired task about using an appropriately hard abrasive. At one end, using an excessively hard abrasive wastes money by wearing it down when a cheaper, less hard abrasive would suffice. At the other end, if the abrasive substance is too soft, abrasion does not take place in a timely fashion, effectively wasting the abrasive as well as any accruing costs associated with loss of time.


Other instances of abrasion

Aside from the aforementioned uses of shaping and finishing, abrasives may also be used to prepare surfaces for application of some sort of paint of adhesive. An excessively smooth surface may prevent paint and
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s from adhering as strongly as an irregular surface could allow. Inflatable tyre repair kits (which, on bicycles particularly, are actually patches for the inner tube rather than the tyre) require use of an abrasive so that the self- vulcanising
cement A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixe ...
will stick strongly. Inadvertently, people who use knives on glass or metal
cutting board A cutting board (or chopping board) is a durable board on which to place material for cutting. The kitchen cutting board is commonly used in preparing food; other types exist for cutting raw materials such as leather or plastic. Kitchen cutting bo ...
s are abrading their knife blades. The pressure at the knife edge can easily create microscopic (or even macroscopic) cuts in the board. This cut is a ready source of abrasive material as well as a channel full of this abrasive through which the edge slides. For this reason, and without regard for the health benefits, wooden boards are much more desirable. A similar occurrence arises with glass-cutters. Glass-cutters have circular blades that are designed to roll not slide. They should never retrace an already effected cut. Undesired abrasion may result from the presence of
carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...
in
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal co ...
s. While smaller particles are readily transported by the lubrication system, larger carbon particles may abrade components with close
tolerances Engineering tolerance is the permissible limit or limits of variation in: # a physical dimension; # a measured value or physical property of a material, manufactured object, system, or service; # other measured values (such as temperature, hum ...
. The carbon arises from the excessive heating of
engine 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, detergen ...
or from incomplete combustion. This soot may contain fullerenes which are noted for their extreme hardness—and small size and limited quantity which would tend to limit their effect.


See also

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Abrasion (mechanical) Abrasion is the process of scuffing, scratching, wearing down, marring, or rubbing away. It can be intentionally imposed in a controlled process using an abrasive. Abrasion can be an undesirable effect of exposure to normal use or exposure to t ...
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Abrasive blasting Sandblasting, sometimes known as abrasive blasting, is the operation of forcibly propelling a stream of abrasive material against a surface under high pressure to smooth a rough surface, roughen a smooth surface, shape a surface or remove su ...
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Erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...
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Steel abrasive Steel abrasives are steel particles that are used as abrasive or peening media. They are usually available in two different shapes (shot and grit) that address different industrial applications. Steel shot refers to spherical grains made of molt ...
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Tribology Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. Tribology is highly interdisciplinary, drawing on many academic fi ...
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Wear Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear in ...


References


External links

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Metal and Composite Finishing Inc., Abrasive Technical Information
{{Authority control Materials with minor glass phase Metalworking Woodworking Carving Stone (material)