Power grinders come in different sizes and speed ranges. The size of a power grinder is normally determined by the diameter of the largest grinding wheel or disc that can be fitted to it.
Grinding wheels and discs usually have a maximum safe operating speed printed on them. This maximum speed must never be exceeded or the wheel or disc could disintegrate.
Every well-equipped workshop has a solidly mounted grinder, either on a pedestal bolted to the workshop floor, or securely attached to the workbench.
Appropriate eye protection must be worn when grinders are being used, and the wheel guards must be correctly and firmly in place.
A bench grinder or pedestal grinder normally has a rating with the size of the grinding wheel it can take. Bench or pedestal mounted grinders take grinding wheels in grades from coarse to very fine, depending on the size of the abrasive grains that are bonded together to make the wheel. They also range in hardness, depending on the abrasive used and the material that bonds the particles together. If a particular grinding application is required, a check should be done to find out the most suitable grinding wheel for it.
A straight grinder or more commonly, an angle grinder is needed when the bench grinder is not appropriate. The straight grinder takes conventional grinding wheels, just like the stationery grinders, although they're limited to a grinding wheel diameter of about 125 millimeters or 4 3⁄4 inches.
The angle grinder uses discs, rather than wheels. During grinding, the face of the disc is used instead of the edge. There are special discs that can fitted to these machines that can be used for cutting. They use the edge of the wheel and are useful for jobs that can’t be reached with a hacksaw.