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Scotch Brite

SCOTCH BRITE HAND PADS UNTUK BERANEKA RAGAM APLIKASI INDUSTRIAL

Scotch Brite handpads dapat digunakan untuk aplikasi deburing , blending , scuffing, finishing, cleaning dan surface preparation pada material metal , stainless steel, kayu , plastic , aluminium , melamine , dll. Memberikan hasil akhir yang lebih baik, mencegah terjadinya pengamplasan material yang berlebihan, menghilangkan geram-geram ( bur ) pada benda kerja dengan hasil akhir yang konsisten , mudah dibersihkan untuk digunakan kembali, tahan lama , serta akan menghemat biaya pekerjaan dibandingkan dengan amplas / alat lainnya seperti steel wool, sikat kawat , sanding  sponges dan amplas lembaran , razor blade , ataupun cairan chemical.

tersedia dalam beberapa type :

-Type F White   ,  Scotch Brite  7445

-Type A Maroon , Scotch Brite  7447

-Type S  Grey    ,  Scotch Brite  7448

Tersedia dalam bentuk :

-Scotch brite Hand pad  6″ x 9″

-Scotch Brite Roll

-Scotch brite Rolloc

-Scotch Brite Belt

-Scotch Brite Disc

Choose and Use Non-Woven Abrasives

How To Choose and Use Non-Woven Abrasives

Abrasive products are usually categorized as bonded abrasives and coated abrasives, but there is a third category that prepares and applies a final finish to the surface, these are non-woven abrasives . . .

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Abrasive products used for finishing metal and non-metallic work pieces are generally categorized into two main groups: bonded abrasives (usually grinding wheels) and coated abrasives (belts, discs, sheets, etc.). These products are used to remove stock during the production process. But there is a third category of abrasives that serve a specialized and highly necessary function of preparing and applying the final surface finish, which can be critical to the performance and appearance of the work piece. These are non-woven abrasives.

These products are manufactured using a web of nylon fibers that are bonded together with synthetic resins. The fibers are impregnated with abrasive grain, producing a durable, cushioned, three-dimensional material that is pliable and conformable to the work piece.

Non-woven abrasives can be ideal for deburring, cleaning and imparting the desired finish to a variety of materials. A basic understanding of how these products are made and how they should be selected and used to their maximum benefit can help the metalworking manufacturer achieve the desired surface finish.

Role of Non-Woven Abrasives

The job of non-woven abrasives begins where other grinding products leave off. The relatively non-aggressive nature of nylon and the abrasive grit used in non-wovens make them excellent finishing tools.

The roll-on, roll-off system

Flap wheels are highly conformable to the work piece and can be used on a broad range of materials.

With their open mesh construction, non-wovens are waterproof, washable and resilient. They resist loading and rusting and are nonconductive.

In the standard non-woven design, abrasive grain is uniformly dispersed throughout the nylon web, providing a continuous supply of new grain as the old grain and fibers wear away during use. While 60-80 grit abrasives are considered intermediate sizes in other products, they are considered coarse for non-woven products.

Non-wovens can be used on a range of metals, including aluminum, brass, copper, nickel, chrome plate, stainless steel and titanium, as well as other hard-to-grind materials such as ceramic, glass and plastic. Used wet or dry, non-wovens enable the user to achieve a consistent, uniform finish and conformability to irregular surfaces with minimal smearing and discoloration of the work piece.

Components of Non-Woven Abrasives

While non-wovens are made differently from conventionally coated abrasives, both products use many of the same abrasive minerals. Silicon carbide is sharper, cutsfaster and produces finer scratch patterns on most surfaces. Aluminum oxide is more durable and lasts longer. It is also more aggressive on hardened steel parts and produces less discoloration on aluminum.

Grit refers to the size of the abrasive grain impregnated into the nylon web (the lower the number, the larger the grains). Use of large particles (coarse grit) results in a more aggressive cut and a coarser finish. Smaller size particles in a non-woven product produce a fine surface finish, if all other conditions are equal.

Grit Designation

Comparable Grit Mesh

Coarse (C)
Medium (M)
Fine (F)
Very Fine (VF)
Ultra Fine (UF)
Micro Fine (SF)

50-80
100-150
180-220
240-360
600
1000-1200

In specifying a conventional bonded or coated abrasive product, the purchaser selects a specific grit size, for example 120 grit. With non-woven abrasives, one of the following designations is used:

Density is another term used in specification that may be unfamiliar to someone who buys conventional abrasives. This refers to the amount of bonding agents and abrasive grain that have been compressed into the non-woven product. In general, harder density products cut faster, last longer and produce finer finishes than softer density products. However, softer densities offer more conformability to the work surface and less tendency to load or burn the work piece.

Sizing and bonding agents are two other factors in the design and manufacture of non-woven abrasives. Fiber size has a significant effect on the product’s cutting characteristics, while the type of waterproof resin used to bond the fibers together and anchor the abrasive to the web can alter the characteristics of the product. The non-woven manufacturer selects the appropriate fiber size and bonding agent based on the intended application for the product; therefore, these components are not included in the product offering specifications.

A typical specification on a non-woven abrasive product might look like this:      8 A/O MED
The first symbol, 8, in this example, refers to the product’s density. This can range from 2 (open/most conformable) to 9 (densest/most durable).
The second symbol, A/O, denotes the abrasive used. A or A/O refers to aluminum oxide.
The final designation, MED, denotes the grit size of the product.

Products Designed for Application Needs

The basic non-woven design lends itself to a variety of product types that meet a range of needs for metalworking and finishing. In general, non-woven abrasive products can be categorized into hand pads, rolls, discs, belts and wheels.

Hand pads are designed to provide excellent conformability and flexibility when hand finishing the work surface. They are generally available in 6 × 9 inch sizes, but are easily folded into smaller sizes as needed.

Role of Non-Woven Abrasives

The roll-on, roll-off system

Unified wheels are ideal for deburring, polishing, cleaning and finishing metals and composites with hard-to-reach areas and can be shaped to match the part.

Grit sizes range from coarse grit used in general cleaning to micro-fine grit for light scuffing and blending. In wet applications many users choose a non-woven hand pad as a replacement for steel wool because non-wovens are nonmetallic and therefore do not rust.

Rolls can be used for broader applications. Offering a more convenient source of the same cleaning and finishing performance as hand pads, rolls are available in 30-ft lengths and widths of 4 and 6 inches. The user simply cuts the roll to the required size for hand sanding or jitterbug sanding applications.

Non-woven discs come in a variety of designs for many cleaning and finishing applications. Arbor hole discs are used on high-speed grinders. Extra coarse grit products may be used for removing surface rust and residue, corrosion, light weld splatter and other surface contaminants. These discs can also be ganged with spacers to form a wide wheel used for sharp edge radiusing or deburring a decorative finish.

Right-angle discs are used on portable grinders for cleaning, deburring, blending and finishing, as well as for removing light rust, oxidation and coatings. The latest advance in grinding for these applications is the development of see-through discs for right angle grinding. These discs feature a specially shaped triangular profile and holes in the discs and back-up pads. This provides the operator with a clear view of the cutting surface, resulting in more controlled stock removal and a better surface finish. The holes also serve to disperse heat and loosen grinding material for a cooler finish and less power draw.

Non-woven belts are used on portable, bench and pedestal bench machines as an effective alternative to coated abrasive belts for cleaning, buffing and polishing. The conformability of the belts result in minimal gouging of the work piece, generating a more consistent finish.

Non-woven wheels

1. Flap wheels are fabricated by mounting sheets of non-woven material around a center hub. The tightly packed pieces form the spokes of a wheel. This is the best choice where conformability to a surface or a long-line brushed finish is required.

2. Convolute wheels are made by wrapping the non-woven material around a center core and bonding the layers together. These wheels can easily be shaped to match preformed parts.

3. Unified wheels are formed by compressing multiple layers of non-woven web material and bonding them together to form a wheel. They are ideal for general purpose cleaning and deburring.

Making the Most of Non-Woven Wheels

Of all the non-woven abrasive product types, the wheel family requires the most care in setup and operation. Maximum wheel life and best surface conditioning can be achieved by following these recommendations.

Wheel direction. Convolute wheels must always run the direction indicated by the arrow printed on the side of each wheel. Flap wheels and unified wheels can be run in either direction.

Wheel speed. The speed at which the wheel is run affects product finish, rate of cut and wheel life. Fast wheel speeds generally give harder action and a finer finish. Slower speeds give softer action and a coarser finish. Following are recommended operating speeds for most common applications.

Cleaning/upgrading of surface conditions

2,200-6,000 sfpm

Cut buffing on metal surfaces

6,500-8,000 sfpm

Deburring

5,500-8,000 sfpm

Decorative finishing

500-3,000 sfpm

Imparting decorative finishes

900-3,000 sfpm

Oxide removal

3,500-6,500 sfpm

Pressure. Light to medium pressure is recommended for most operations. Flap wheels require much lighter pressure to perform properly than other non-woven wheels. Unified wheels can withstand much higher pressures in order to perform deburring jobs. In all cases, avoid excessive pressure, which may result in wheel deformation and damage to the work surface.

Feed speed. Feed speeds directly affect the number of pieces completed over a given time. Slow feed speed reduces the number of completed pieces, while producing a shorter scratch pattern. Slow feed speed also allows for longer dwell time and permits more work to be done on each piece.

The roll-on, roll-off system

Convolute wheels are general-purpose wheels for deburring, blending and polishing. They are smear and heat resistant.

Oscillation. Oscillation may be used to break up scratch lines and produce a more uniform finish. An increase in cut may also be experienced. A general starting point for oscillation is 3/8-inch amplitude at 200 cycles per min.

Lubricants. The use of lubricants, such as water, water-soluble oil and straight oil, will decrease the heat generated while running, improve the luster and reduce the surface finish. The higher the viscosity of the lubricant, the lower the surface finish (RMS value) produced.

This information will assist users in selecting non-woven abrasives to complement their bonded and coated abrasives. However, it is important to remember that changes in any one of the many factors discussed here can affect the surface finish of the work piece. Work in partnership with your supplier to make the best product and application choices by considering every facet of your operation. By taking this system approach, you will maximize the productivity of your non-woven abrasives applications.

Abrasive / Amplas

Coated Abrasive atau yang lebih umum dikenal dengan nama Amplas ( hampelas , abrasives ) banyak digunakan untuk segala macam pekerjaan dari pekerjaan pengamplasan kasar hingga pekerjaan yang menghasilkan kilau/kilap yang sangat tinggi. Produk amplas mempunyai unjuk kerja yang sangat mengagumkan dibandingkan dengan produk amplas , abrasive lainnya, sebab produk amplas abrasive , abrasives membantu mempertahankan standar kualitas yang paling tinggi dan memberikan hasil yang sangat konsisten. Sebagai contoh, dengan menggunakan beberapa product amplas abrasive maka akan memberikan hasil yang sangat bersih pada permukaan benda kerja sehingga akan memberikan daya melekat yang baik sekali bila dilapisi oleh suatu coating. Mempunyai kemampuan untuk mencegah tertempelnya debu hasil pengamplasan pada amplas ( abrasive , abrasives ) sehingga meningkatkan produktivitas. Pada akhirnya biaya dapat ditekan sebab amplas ( abrasive ) yang dipakai lebih tahan lama. Cakupan produk amplas ( abrasive , abrasives ) terdiri dari yang berbasis kertas, kain, kombinasi, poliester film, dan fiber. Dengan perekat yang digunakan berupa Glue, Resin dan Waterproof. Partikel amplas ( abrasive ) yang digunakan meliputi : Aluminum Oksida, Silikon Karbida, Alumina Zirconia, Sintetis Diamond, dan Cubitron yang merupakan penemuan untuk mineral Ceramic Aluminum Oxide.

Rolls

Abrasive / amplas Cloth Roll dirancang untuk memenuhi produksi dan aktivitas maintenance Anda. Produk ini dibuat dari bahan yang sangat fleksibel dan dilapisi dengan alumunium oksida. Cocok dipakai untuk aplikasi yang memerlukan fleksibilitas yang tinggi. Produk ini dapat langsung dipergunakan dengan tangan atau pengoperasian dengan mesin.

Sheet

Abrasive Paper Sheet adalah produk abrasive / amplas yang dibuat dari bahan alumunium oksida dan memiliki backing kertas yang sangat fleksibel. Produk Fre-Cut ini sangat cocok digunakan untuk aplikasi woodworking serta pengerjaan untuk kondisi kering. Sedang untuk pemakaian pada kondisi basah dan aplikasi umum lainnya, dapat menggunakan utility paper yang memiliki backing tahan air.

Stikit Disc

Stikit Abrasive /Amplas ( abrasives ) yang memakai lem :

Digunakan untuk bermacam-macam benda seperti Kayu Lunak, Kayu Keras, Besi, Plastic, Serat Kaca, Lapisan Cat/Lapisan Dasar, dan Marmer/Batu Sintetis.

Amplas ( abrasive ) berkualitas tinggi dengan lapisan lem di bagian belakang masing-masing amplas ( abrasive ).Tersedia dalam bentuk Disc Roll. Bekerja sangat cepat dengan menggunakan mesin Sander tipe Orbital.

Flexible Grinding Disc

Flexible Grinding Disc atau batu gerinda mempunyai ciri khas yaitu mempunyai kemampuan yang fleksibel dibandingkan dengan yang lainnya. Menggunakan mineral aluminum oksida yang lebih maju untuk memberikan kemampuan yang lebih fleksibel, daya potong yang lebih besar dan usia pakai yang lebih lama dibandingkan dengan batu gerinda / Grinding Disc lainnya. Produk ini sangat membantu meningkatkan produktivitas dan menurunkan biaya operasi. Cocok untuk pekerjaan – pekerjaan normal seperti grinding / mengerinda, polishing dan finishing.Tersedia dalam ukuran berdiameter 4 inci dan 7 inci .

Roloc

Roloc Disc mempunyai ciri khas khusus yaitu kancing berulir pada ujung disc yang digunakan untuk memudahkan membuka dan mengencangkan disc pada dudukannya. Dengan hanya memutar sedikit saja, amplas ( abrasive , abrasives ) yang mengunakan sistem roloc akan terkunci dengan sempurna. Roloc disc ini sangat sesuai untuk mengerinda daerah-daerah yang kecil atau sempit.

Flap Disc

Flap Disc adalah amplas ( abrasive , abrasives ) yang disusun seperti kipas yang berbentuk bulat. Produk ini memberikan laju pemotongan yang konsisten dengan finishing yang mengagumkan dan memberikan unjuk kerja yang tahan lama yang dapat meningkatkan kualitas dan menurunkan biaya anda.

Fiber Disc

Fiber Disc dirancang untuk aplikasi gerinda. Tersedia dalam ukuran 4 inch dan 7 inch dengan menggunakan mineral yang khusus untuk dipakai pada mineral atau metal yang khusus.

Abrasive

Abrasive / abrasives is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away. While finishing a material often means polishing it to gain a smooth, reflective surface it can also involve roughening as in satin, matte or beaded finishes.

Abrasives / amplas 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 abrasive / abrasives as well as the shape of the abrasive / amplas. Common uses for abrasive / abrasives include grinding, polishing, buffing, honing, cutting, drilling, sharpening, and sanding (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 act by abrasion but are not classed as abrasive / abrasives as they are a shaped bar of metal. However, diamond files are a form of coated abrasive (as they are metal rods coated with diamond powder).

Abrasive / Abrasives give rise to a form of wound called an abrasion or even an excoriation. Abrasions may arise following strong contract with surfaces made things such as concrete, stone, wood, carpet, and roads, though these surfaces are not intended for use as abrasives.

Contents

* 1 Mechanics of abrasion

* 2 Abrasive minerals

* 3 Manufactured abrasives

o 3.1 Bonded abrasives

o 3.2 Coated abrasives

o 3.3 Other abrasives and their uses

* 4 Choice of abrasive

* 5 Other instances of abrasion

* 6 References

* 7 See also

Mechanics of abrasion

Abrasive / Abrasives generally rely upon a difference in hardness between the abrasive / abrasives and the material being worked upon, the abrasive / abrasives being the harder of the two substances. However, this is not necessary as any two solid materials that repeatedly rub against each other will tend to wear each other away (such as softer shoe soles wearing away wooden or stone steps over decades or centuries or glaciers abrading stone valleys).

Typically, materials used as abrasive / abrasives are either hard minerals (rated at 7 or above on Mohs scale of mineral hardness) 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, a common abrasive / abrasives , for instance occurs both naturally and is industrially produced , as is corundum which occurs naturally but which is nowadays more commonly manufactured from bauxite.[1] However, even softer minerals like calcium carbonate are used as abrasive / abrasives, such as “polishing agents” in toothpaste.

Grit size ranging from 2 mm (the large grain) (about F 10 using FEPA standards) to about 40 micrometres (about F 240 or P 360).

Grit size ranging from 2 mm (the large grain) (about F 10 using FEPA standards) to about 40 micrometres (about F 240 or P 360).

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 / abrasives . 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. The abrasive / abrasives 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 / abrasives.

Some factors which will affect how quickly a substance is abraded include:

* Difference in hardness between the two substances: a much harder abrasive / abrasives 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 / abrasives and cast off work material tends to fill spaces between abrasive / abrasives grains so reducing cutting efficiency while increasing friction

* Use of lubricant/coolant/metalworking fluid: Can carry away swarf (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

Abrasive / Abrasives may be classified as either natural or synthetic. When discussing sharpening stones, natural stones have long been considered superior but advances in material technology are seeing this distinction become less distinct. Many synthetic abrasive / abrasives are effectively identical to a natural mineral, differing only in that the synthetic mineral has been manufactured rather than been mined. Impurities in the natural mineral may make it less effective.

Some naturally occurring abrasives are:

* Calcite (calcium carbonate)

* Emery (impure corundum)

* Diamond dust (synthetic diamonds are used extensively)

* Novaculite

* Pumice dust

* Rouge

* Sand

Some abrasive / abrasives minerals (such as zirconia alumina) occur naturally but are sufficiently rare or sufficiently more difficult/costly to obtain such that a synthetic stone is used industrially. These and other artificial abrasive / abrasives include:

* Borazon (cubic boron nitride or CBN)

* Ceramic

* Corundum (alumina or aluminium oxide)

* Dry ice

* Glass powder

* Silicon carbide (carborundum)

* Zirconia alumina

Manufactured abrasives

Abrasive / Abrasives are shaped for various purposes. Natural abrasives are often sold as dressed stones, usually in the from 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

Assorted grinding wheels as examples of bonded abrasives.

A grinding wheel with a reservoir to hold water as a lubricant and coolant.

A bonded abrasive is composed of an abrasive material contained within a matrix, although very fine aluminium oxide abrasive may comprise sintered material. This matrix is called a binder and is often a clay, a resin, a glass or a rubber. This mixture of binder and abrasive is typically shaped into blocks, sticks, or wheels. The most usual abrasive used is aluminium oxide. Also common are silicon carbide, tungsten carbide and garnet. 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 / abrasives and workpiece often makes necessary the use of a lubricant of some kind. Traditionally they were called coolants 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 tools used in precision work, such as scale modelling.

Bonded abrasives need to be trued and dressed after they are used. Dressing is cleaning the waste material (swarf and loose abrasive / abrasives ) from the surface and exposing fresh grit. Depending upon the abrasive and how it was used, dressing may involve the abrasive / abrasives being simply placed under running water and brushed with a stiff brush for a soft stone or the abrasive / abrasives being ground against another abrasive / abrasives , 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 German sandpaper showing its backing and FEPA grit size.

Main article: Coated abrasive

A coated abrasive comprises an abrasive fixed to a backing material such as paper, cloth, rubber, resin, polyester or even metal, many of which are flexible. Sandpaper is a very common coated abrasive / abrasives . Coated abrasives are 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 matchboxes, on diamond plates and diamond steels. Diamond tools, though for cutting, are often abrasive in nature.

Other abrasives and their uses

Here the abrasiveness of toothpaste is detailed by its Relative Dentin Abrasivity (RDA)

Sand, glass beads, metal pellets and dry ice may all be used for a process called sandblasting (or similar, such as the use of glass beads which is “bead blasting”). Dry ice will sublimate meaning that there is no residual abrasive left afterwards.

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 silverware and optical media. The liquid, paste or wax acts as a binding agent that keeps the abrasive / abrasives attached to the cloth which is used to as a backing to move the abrasive across the workpiece. 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 contains calcium carbonate or silica 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 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, tile, metal or stone surfaces. However, many laminate 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 / abrasives.

Metal pots and stoves are often scoured with abrasive cleaners, typically in the form of the aforementioned cream or paste or of steel wool.

Human skin is also subjected to abrasion in the form of exfoliation. Abrasive / Abrasives for this can be much softer and more exotic than for other purposes and may include things like almond and oatmeal. Dermabrasion and microdermabrasion are now rather commonplace cosmetic procedures which use mineral abrasive / 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), after which 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 / abrasives 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 / abrasives to achieve a basic shape, and then have finer grades of abrasive successively appied 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 (when the abrasive or workpiece is a silicate) 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 / abrasives 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 scratched optics and compact discs or a dull knife);

* trap dirt, water, or other material;

* increase surface area (permitting greater chemical reactivity such as increased rusting 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 pistons).

A finer or softer abrasive / abrasives 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 tends to cut less deeply than a coarser, harder material. Also, the softer abrasive / abrasives 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 for a cut-throat razors, however, the purpose of stropping is not to abrade material but to straighten the burr on an edge. The final stage of sharpening Japanese swords 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 / abrasives.

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 / abrasives.

Thought must be given to the desired task about using an appropriately hard abrasive / abrasives. At one end, using an excessively hard abrasive wastes money by wearing it down when a cheaper, less hard abrasive / abrasives would suffice. At the other end, if 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, abrasive / 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 adhesives 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 / abrasives so that the self-vulcanising cement will stick strongly.

Inadvertently, people who use knives on glass or metal cutting boards 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 / abrasives through which the edge slides. For this reason—without regard for the health benefits—wooden boards are much more desirable. A similar occurrence arises with glass-cutters. Glass-cutters are 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 in internal combustion engines. While smaller particles are readily transported by the lubrication system, larger carbon particles may abrade components with close tolerances. The carbon arises from the excessive heating of engine oil 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.

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