Abrasives are a type of material used to polish, smooth out, clean or even shape surfaces and other materials. They are widely used in industrial wood- and metalworking, but they can also be found in homes as cleaning products.
How Abrasives Work
To make an abrasive work, a user simply needs to rub the coarse or rough side of the material onto the surface or object being worked on. You can think of one piece of grit of an abrasive substance as one tiny cutting device. With thousands of pieces of grit covering an abrasive material, it can scrape or rub off the surface of most other materials, such as wood or metal.
An abrasive material is graded according to the coarseness of its particles, or pieces of grit. A coarser grit would mean that the abrasive is very rough and ideal for removing large quantities of wood or metal surfaces. Such material is appropriate for shaving, shaping or grinding procedures. Meanwhile, a finer grit results in a smoother abrasive, making it suitable for finishing or polishing jobs. In practice, fine abrasives are used after working with coarse ones. This is to ensure a smoother and high-quality finish, particularly on wood surfaces.
Substances Used to Make Abrasives
The substances used in making abrasive materials can be classified as either natural or manufactured. Natural materials include glass, emery, pumice and diamond dust. Meanwhile, some examples of manufactured materials are glass, nylon, aluminum oxide and other substances that are combined with chemical- or aluminum-based components. Other popular materials used include steel alloys, zirconia and garnet.
Apart from the hardness of the grits, or particles, an important characteristic of a good abrasive substance is its sharpness. For work on metal surfaces that are considered nonferrous, an abrasive made from silicon carbide is ideal. Meanwhile, for ferrous metals, you can opt to use aluminum oxide abrasives. Diamond abrasives are used in grinding and polishing ceramic materials.
Common Types of Abrasives
1. Bonded or Fused Adhesives
Most industrial-grade abrasives are made from two or more materials that are combined via the application of heat, resin adhesives or other forms of binders. Not only are they made from different materials, but they are also worked up into different shapes, like blocks, wheels and cones. The two best examples of a fused abrasive material are the artificial sharpening stone and the modern grinding wheel.
2. Abrasives Bonded in a Metal Matrix
Some abrasive tools are coated with metal composites. Certain metal composites are designed to wear away and expose the main abrasive material during use. The metal composites can prevent the main abrasive material from prematurely losing its sharpness. Most diamond abrasives used for working on ceramic or glass materials are bonded in a metal matrix.
3. Coated Abrasive Materials
The abrasive particles in this type of material are glued onto a flexible supporting component, usually paper, fiber or cloth. The particles are bonded using resins that are heated at a high temperature. Sandpaper is the most popular example of a coated abrasive.
These abrasives are designed for precision work. They are small in size and have very fine protruding abrasive edges or tips. The grits used in burrs are usually made from diamonds or tungsten carbide. Burrs are widely used in dentistry, where they take the form of a rotary tool that is put to work when removing or scraping off decayed teeth parts. They are also used to enlarge teeth cavities in preparation for the application of dental fillings.
5. Nylon Abrasives
In its most basic form, this type of abrasive is made of woven nylon material. In certain varieties, the nylon component is laced or covered with other abrasive particles. Nylon abrasives have numerous applications. They can be used in industrial settings, but they can also take the form of cleaning or scouring pads used in most homes.
6. Powder or Paste Abrasives
Also referred to as a lapping compound, this type of material is basically made up of very fine abrasive particles. Powder abrasives are ideal for finishing or polishing jobs. Some lapping compounds also come in paste rather than powder form.
Typical Uses of Abrasives
Wood product companies are among the biggest users of abrasive materials. When working with wood surfaces, the abrasive material you use is vital for achieving the desired finish. Yet since wood is more delicate compared to metals and other types of materials, you need to choose the type of abrasive to use carefully.
The cheapest material you can use is regular sandpaper. Fine wood craftsmen opt for flint sandpaper, as it is tougher and its sharpness can last for several uses. Before aluminum oxide became popular, garnet sandpaper was also a favorite among woodworkers because of its sharpness that can minimize unwanted scratches on wood surfaces.
Manufacturers of metal products use abrasives at the start of the production to break up large pieces of newly cut metals. This process is known within the industry as deburring, and it involves repeatedly rolling the metal parts in a big rotating tub that contains the abrasives. Sometimes, abrasive materials are again used at the end of production to polish the semi-finished metal products.
3. Jewelry Manufacturing
Most gemstones that are used in jewelry undergo abrading processes. For minerals like diamonds, abrasive materials are used to cut them into proper sizes and shapes. Polishing other types of precious stones may require a very delicate procedure in which unconventional materials like ice, plastic beads and even walnut shells are used as abrasives.
4. Industrial or Professional Cleaning
Industrial or professional cleaners use a process called pressure blasting. This involves the forceful application of abrasive materials like sand, glass or plastic grits onto the surface of the objects being worked on. The high-pressured flow of abrasives is effective in scraping away dirt, rust and other unwanted materials. Pressure blasting provides a more consistent finish compared to other professional cleaning methods.
5. Sharpening Tools
Apart from cleaning and polishing surfaces, abrasives can also be used for sharpening a wide variety of tools. Many high precision tools require diamond paste to retain their sharp edges. Referred to as bort, diamond in this form is effective in grinding and cutting jobs. Bort can also be fused onto sharpening files.