A grinding wheel is a wheel composed of an abrasive compound and used for various grinding (abrasive cutting) and abrasive machining operations. Such wheels are used in grinding machines. Grinding wheels are consumables, although the life span can vary widely depending on the use case, from less than a day to many years. As the wheel cuts, it periodically releases individual grains of abrasive, typically because they grow dull and the increased drag pulls them out of the bond. Fresh grains are exposed in this wear process, which begin the next cycle. The rate of wear in this process is usually very predictable for a given application, and is necessary for good performance.
A grinding wheel consists of three basic elements: abrasive (grains), bond and pores. The type and combination of these three elements result in very different grinding wheels.
The grains should be as hard and tough as possible, to ensure stock removal from the workpiece. The size of the grain can vary in any of these four categories. The following generally applies: The smaller and finer the grain, the finer the surface of the workpiece will be (and vice versa). In addition, a rougher-grained grinding wheel is normally used for pre-grinding and a finer grained grinding wheel is used for finish-grinding.
The bond is necessary to hold the grains together in the wheel. It determines the hardness, strength and cutting ability of the grinding wheel.
The pores are determined by the relationship between grains and bond. They are responsible for the removal of chips and for transport of the cooling lubricant to the workpiece.
Soft grinding wheels should be used for hard materials and vice versa. The hardness of a grinding wheel is primarily determined by the bond. When hard materials are ground with soft grinding wheels the grains break out, so that new easy-cutting grains are used again.