It is well known that one material is able to erode the other when they both come in contact with each other. Abrasive is any material which is used through roughening, polishing and rubbing in finishing and shaping a working material, this results in the working material to be worn out by friction.
WHAT ARE THEY MADE UP OF?
Abrasives are of natural or synthetic origin and their degree of hardness are what mainly differentiates them. They are made from minerals that are present in small size or can be into tiny particles known as grit for them to be used. Diamond is the hardest abrasive material naturally present, others such as zirconium, carbide, corundum etc can occur both as natural or artificially made, their level of hardness cannot be compared to diamond.
Some naturally occurring abrasives are:
- Calcite (calcium carbonate)
- Emery (impure corundum)
- Diamond dust (synthetic diamonds are used extensively)
- Powdered feldspar
Artificial abrasives include
- Borazon (cubic boron nitride or CBN)
- Ceramic aluminium oxide
- Ceramic iron oxide
- Corundum (alumina or aluminium oxide)
- Dry ice
- Steel abrasive
- Silicon carbide (carborundum)
- Zirconia alumina
- Boron carbide
Abrasive tools are made using a support such as canvas or paper with a glue or resin which the abrasive is being attached to. To make more complex abrasive instruments, the procedures are very different as it involves the use of industrial machinery. Examples of some abrasives includes; paper sheets(sandpaper), abrasive discs,strips,flap wheels etc.
Both natural and synthetic abrasives can be seen in different shapes based on the purposes at which they are going to be used for. Natural are usually seen in block or stone form.
There are two types of abrasives;
These kinds of abrasives are composed and contained in a matrix which is a binder in the form of resin, glass,rubber or clay. The most commonly used minerals for this kind of abrasives are silicon carbide, tungsten carbide, garnet and aluminium oxide.
After use this type of abrasive needs to be dressed that is cleaning off any waste material left and trued which is restoring back to its normal shape.
This type of abrasive is usually attached to a backup material which are sometimes quite flexible and can be seen attached to metals, rubber, resin, paper, cloth, and even polyester. The most commonly used coated abrasive is the sandpaper. They can also be shaped into various hand used machines and power tools such as handpads, orbital and rotary sanders, belt grinders, and also wrapped around sand blocks.
Abrasives are easily seen and are used widely in various domestic, technological and industrial applications, this brings about a huge difference in the aspect of shape as well as in the properties of the abrasives which include physical and chemical composition. Some of the basic uses of abrasives include cutting, drilling, grinding, honing, sharpening, buffing, lapping, polishing, sanding and polishing.
- For industrial processes, many common objects are made as seen in the bodywork of cars. When the pieces used to make up car parts are put together by welding, the metal junctions become rough and burring, abrasive materials are then used to remove this metal burr. This makes them important in automotive and metallurgical sectors.
- In myriad industries, that deals with wood, metal and cleaning work, sandpaper is mostly used. Others that are likely used are; Nylon abrasive pads can be reused, pumice stone and steel wool are both good in smoothening and finishing lacquer and also coats of varnish respectively.
- Abrasives are also used in metalworking for various purposes, In deburring, it is used to grind freshly cut metal. Abrasives such as coated abrasives, like nonwoven products and stones, also sandpaper can be used. Abrasives such as hard minerals like diamond and synthetic minerals can be used to polish finished products. In desperate situations almost anything can be used as an abrasive like plastics, nuts shells, ice. Etc.
- Also professionals and artisans also use abrasives for certain operations like furnishing and some extraordinary works of art, cutting stainless steel, carpenters use it for finishing surfaces of parquet to obtain a matte or glossy look as needed.
HOW TO CHOOSE AN ABRASIVE.
Abrasives differ mainly in sizes, grains and shapes, and so are used in different kinds of processes. They exist in the form of wheels, cutters, various files and discs etc.
However, choosing and using the right and suitable shaped abrasive is important for working a surface and thereby achieving the best result. For example; In flat surfaces, conical abrasive discs allows one to get greater precision and to work on a larger surface while flat abrasive discs provide more aggressiveness during abrasion on a narrow surface. and flat abrasive discs can be used both flat and conical abrasive discs can be used on flat surfaces. The first offers a more aggressive abrasion on a narrow surface, while the second allows you to work on a larger surface and with greater precision. Cup shaped abrasives are advised for shaped or corner surfaces.
Factors that can affect abrasion processing are;
- Difference in hardness between the two substances: a much harder abrasive will cut faster and deeper
- The Grain size (grit size): larger grains will cut faster as they also cut deeper
- Adhesion that exist between the grains and backing, and between grains and matrix; This determines how fast grains are lost and when new ones are being exposed
- Contact force as high force brings about quicker abrasion.
- Worn out abrasive if not replaced causes friction which can slow down abrasive processes.
- Use of lubricant/coolant/metalworking fluid:
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