Ground down with abrasives - we can help you; diamond!
Abrasive - what are the different sorts of abrasives and how do they work?
Abrasive is a word for a harder substances that is used for rubbing off material from softer surfaces. The abrasive effect is produced almost entirely by the physical process of the harder substance shearing off or fracturing fragments from the softer substance. In metals, these softer fragments are oxidized by air which stops them from welding themselves back on.
Abrasives are used in three ways:
- The abrasive material is directly applied to the object (for example a knife being sharpened on a grinding wheel)
- The abrasive material is used to coat a secondary substance and that is applied to the surface to be abraded (sandpaper and emery cloth are examples of this)
- The abrasive material is blasted en-masse (for example sandblasting or grit blasting).
Apart from their use in sharpening-stones and grinding wheels, direct-action abrasives are also used in powder form. Most domestic cleaning agents (except soap and washing powder) contain at least one abrasive (usually silica, pumice or finely-ground aluminum oxide). The chemical action of the cleaning agent is helped by the abrasive, and the two substances operating together clean faster than either would have done if used alone.
Toothpaste also contains a mild abrasive which is generally finely-powdered chalk. Old-fashioned tooth powder often contained powdered pumice or silica, which wore the enamel off the teeth in a short time but manufacturers now claim that the cleaning action of their products is mostly chemical.
Most abrasives used in industry are applied indirectly by being stuck to backing. This works out cheaper because less materials are used that way.
The simplest type of coated abrasive material is sandpaper, which is made by simply gluing granules of abrasive material to a sheet of paper.
Abrasive papers are made in a vast range of types, and have many uses. One unusual application is in the printing industry where a sheet that is to be printed on both sides is laid on a sheet of abrasive paper called tympan (rough side up) while the second side is printed. In this way, the already printed side can rest on the abrasive points, which hold it steady and prevent the wet ink from smearing.
Belts coated with abrasives are used in many industrial sanding machines. These cannot be made of paper, which would tear, so a fine, strong cloth such as linen or gabardine is used.
Sand, Emery, Pumice, Silica, Carborundum, Aluminum Oxide and Diamond are harder materials that are all used as an abrasive.
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