An abrasive is a material / mineral used to smooth, polish, cut, grind, another substance This is a common mineral used widely in technological & industrial applications. Natural abrasives consist of pumice, corundum , sand and ground quartz. Alumina (aluminum oxide) and Carborundum (silicon carbide) are synthetically formed abrasives. The hardest abrasives are synthetic or natural diamonds used in the form of dust or minuscule stones.

Abrasives are basically divided into three types namely coated abrasives, bonded abrasives and super abrasives.

Coated Abrasives
Coated abrasives are used in grinding wheels, abrasive sticks or stones. Grinding wheels are used in an array of applications and industries, whilst abrasive stones or sticks are used for honing internal or external surfaces and sharpening edges. Coated abrasives have grains of abrasives held collectively in a matrix of resin, rubber, glass, or other binders. Abrasive grains of coated abrasives are in different bond types. They are used widely to take out surface materials like ceramics, metal, plastics, glass, and paint.

Different kind of abrasive grains are used by coated abrasives. Aluminum oxide is the common industrial mineral that can be used individually and also with other materials to form ceramic grains. This aluminium oxide when mixed with crocus and emery, we get abrasive suitable for finishing applications. Tungsten carbine, silicon carbide, Garnet, and alumina-zirconia are some sort of abrasive grains. Diamond paste is a Super-abrasive used in ferrous lapping or polishing applications where heat and reactivity are not a factor. Cubic boron nitride of cubic crystal structure provides finer grinding performance on alloy steel and carbon. It has hardness next to diamond.

A few use brazed metal bond between the grains of a metal substrate or the abrasive grains. Shellac, resin, rubber, or glass bond systems are used between the abrasive grains. Silicate is a low-strength bonds that minimize heat generation, lack the life and hardness of vitrified or resin bonds. The structural integrity of this coated abrasives are improved by using a fiberglass mesh or other materials or fibers.

Bonded Abrasives
In Bonded abrasives the abrasive grains of resin, rubber, glass or other binders are held together in a matrix. Like coated abrasives, bonded abrasives too is used in grinding wheels that find use age in a variety of applications and industries and abrasive stones or sticks used to hone internal or external face other than sharpening edges.
The shape of bonded abrasives grinding wheels are flat, cylinder mounted on a pin or mandrel having a raised center with a cone. Other wheels have a cup or bowl shape, depressed center, tapered body and donut or ring shape. They are used to remove surface materials such as glass, plastics, metal, ceramics and paint.

Depressed center wheels saw take out masonry products or metal bars. Cup-shaped wheels are both straight & flared. Relieved or Recessed, wheels may be recessed on only one side or else on both sides. Tapered body wheels with thicker cross-section at the bore become thinner or tapers just before the outer diameter.

Usually grit sizes are of ANSI (U.S.), FEPA (European), JIS (Japanese), or Micron graded standards. With Grit size we can measures the abrasive grains in the matrix or that bonded to a surface. Grits, or Coarse grains remove large amounts of material. Medium grains take out less material and provide an enhanced finish than coarse grits. Fine grits are apt for light finishing and cutting and fine grits improve finish.

Super Abrasives
Super Abrasives have been developed to meet the needs of modern industry Today’s challenging super finishing applications can be determined by super abrasives. Cubic boron nitride or polycrystalline diamond has typically extended life and super grinding productivity. It has wide range of applications from natural stone to advanced metallurgical materials.