Abrasives are products to be applied on other materials (marble, granite or stonework in general). Due to their high hardness, they are used in all kinds of processes, both industrial and domestic.
Abrasives may be natural or artificial products, and are classified according to their level or hardness, which is assessed based on a scale of mineral hardness. Some examples of abrasives are aluminium oxide (alumina), sand, silicon carbide or diamond.
Emery is another type of abrasive used to manufacture several types of grinding wheels and sanding discs which are used to sand and cut materials such as stonework and metal. There are some basic elements that play an important part during the cutting and performance of emery wheels and these are: grain type and size, bond, hardness and its structure or spacing.
Grains are the elements that carry out the cutting and sanding action. Type and size must be taken into consideration when choosing the right grain. There are naturally occurring (such as diamond, emery, sandstone, corundum and quartz) and also manufactured grain types. Generally speaking, they contain large amounts of impurities which could hinder the cutting and sanding action. Manufactured grains are created in electric-arc furnaces using controllable methods in order to ensure that the resulting wheel's quality and features meet the grinder's requirements, using materials such as aluminium oxide, silicon carbide, zirconium, and other ceramics.
Since grains are the most crucial element in any abrasive, choosing the correct grain size is critical. Grain size is denoted by the number of meshes per linear inch of the screen through which the grits pass. Coarse-sized grains are normally used for smooth materials, allowing fast cutting but poor surface finish, and to work on large areas. On the other hand, fine grain sizes are used for hard materials which are fragile and breakable, such as steel, cemented carbide and glass, as well as small work areas and to maintain small sections.