Abrasive grains are available in a wide range of grit sizes and bonding agents. Determining which wheel is right for the job requires considering seven key factors:
- The material being ground
- Grinding pressure
- Required finish and form accuracy
- Area of contact
- Wheel speed
- Coolant use
- Machine/spindle horsepower
The Material Being Ground
The first thing to consider when selecting a grinding wheel specification is the workpiece material type and hardness. Is the material easy or difficult to grind? The relative ease of grinding is a major predictor of the appropriate abrasive type, grain attribute, grit size and bond type for the application.
By convention, aluminum oxide grains are used for grinding ferrous metals, and silicon carbide grains for non-metals and non-ferrous metals. Ceramic and superabrasive grains are compatible with all three types of materials, but are typically meant for specific circumstances where aluminum oxide and silicon carbide perform poorly.
With the grain type is established, material grindability determines many of the other necessary attributes for the grinding wheel. If the material is easy to grind, use a tough, durable grain. Since the material is easy to grind, grains shouldn’t break down too soon or too easily, so the whole grain can be used to maximize wheel life. A coarser grit is best for these materials, as the grains can easily penetrate the material and maximize stock removal. A harder grade (that is, a harder bond between the grains and the wheel) also corresponds to easier grinding, as the bond will prevent the wheel from releasing the grains before they are consumed.
For hard-to-grind materials, reverse these recommendations. Mild, friable grades perform better on these materials, as they fracture more easily and stay sharper. Finer grit sizes improve the ability of the particles to penetrate hard materials and form chips. Because the grits will dull and cause metallurgical damage such as burning if held for too long, soft grades are necessary to release dulled grains and expose the material to sharper ones.
Read more: 7 Key Factors in Choosing a Grinding Wheel
