The precision surface grinder is a machine tool that is capable of working to a fine tolerance of plus or minus 0.002 millimetres, or to around plus or minus one ten thousandth part of an inch in the old imperial measurement scale. This is an extremely high degree of precision and naturally requires a skilled operator to achieve it. Of course, much depends on the material being worked with, as well as the type of grinding wheel being used.
The surface grinder usually has a table where the work piece is attached with the grinding wheel positioned above it. The work piece requiring grinding can be traversed in two horizontal directions, either across the face of the grinding wheel, or longitudinally. By using the two direction operating wheels in tandem, the work piece can be positioned precisely where it is needed.
Grinding of a metallic surface requires the work piece to be firmly attached to the table. This is usually achieved by means of a magnetic chuck that can hold a piece of metal firmly in position while it is being grinded. The magnetic chuck can be either electromagnetic or a permanent magnet type. Naturally, this type of chuck can only work with metals that are attracted to a magnet, which includes all types of steel, the most commonly ground metal.
The material used for the surface face of the grinding wheel is important. These range from diamond at the top of the range, through cubic BN Rod and silicon carbide to aluminium oxide. The most commonly used is aluminium oxide because of its efficiency and it relatively low cost of replacement. Because diamond and cubic boron nitride are very expensive to produce, the wheels normally have a core comprised of a hard, but less expensive material with only the outer surface of the wheel being either diamond or cubic boron nitride.
The extremely high degree of precision achievable with a surface grinder depends largely on the condition of the grinding wheel. For this reason dressers are used to dress the grinding wheels back into peak condition. It is also necessary to use suitable coolant lubrication on the work piece while the grinding operation is in progress. This has a dual purpose: the lubricate the grinded surface and keep temperatures down, as well as the continual removal of swarf, or the unwanted material that has been ground away.
The precision surface grinder can achieve amazingly high degrees of machined accuracy in the right hands. It can usually achieve greater machined accuracy than other commonly used types of machine tool, such as a milling machine or lathe. With the use of specialised computer software, the level of precision becomes almost impossible, and in high demand in today’s world.