Norton Gemini Type 27 right angle grinder wheels are extra thin, for quick cutting action with low kerf loss. Kerf is the material that is lost due to cutting, and is roughly equivalent to the thickness of the wheel. Run the grinder at the highest possible speed marked on the wheel.
Reinforced cutoff wheels are designed to resist breakage caused by severe cross-bending and are required on any operation where the work is not securely clamped. Resin bonds are organic bonds that soften under the heat of grinding, releasing dulled abrasive grains. Because of its forgiving nature, only an organic type bond is used in cutoff wheels. The resin-bonded wheel is more resilient than a vitrified wheel. The manufacturing term for a resin bond wheel is "cured," meaning the wheel has been heated to less than 500 degrees F. Depressed center wheels are flat faced with inset centers and are used for cutting off and portable grinding. The depressed center prevents the tool mandrel from gouging the workpiece. These wheels are typically used on flat workpieces at a slight angle with the workpiece.Depressed center wheels are frequently used with right-angle grinders. Using a harder grade wheel increases wheel life but also increases burn and requires more power, and decreases cut rate. Burn is the effect on a workpiece from thermal stress as abrasive cuts or rubs material away. The damage ranges from discoloration to cracking of the workpiece.
Aluminum oxide is a widely used and versatile abrasive material. It is a tough, fracture- and wear-resistant grit that works well with a broad range of materials, from metals to wood. Aluminum oxide is more durable than silicon carbide and often used for material removal and finishing.