GRAIN
The grains within the abrasive of a cutting wheel are the particles that perform the cutting.
Grains may come in several types. Common types of grains for cutting wheels include ceramic alumina, zirconia alumina, aluminum oxide, and silicon carbide.
- Ceramic alumina: Ceramic alumina performs exceptionally well on steel, stainless steel, and other hard-to-cut metals, including inconel, high nickel alloy, titanium and armored steel. When used and maintained properly, it offers a superior lifespan and cut, and it tends to cut cooler than other grains, so it reduces heat discoloration.
- Zirconia alumina: Zirconia alumina provides superior cutting for steel, structural steel, iron, and other metals, and it is ideal for rail cutting and other heavy-duty applications. It offers a fast cut and a long life and holds up under extreme pressure.
- Aluminum oxide: Aluminum oxide is one of the most common abrasive grains. It provides a fast initial cut rate and consistent performance for steel and other metal.
- Silicon carbide: Silicon carbide is an extremely hard grain that produces very sharp and fast cutting. However, it is also friable, meaning it is not as tough as other grains.
The grain's grit helps determine its physical and performance properties as well. The grit refers to the size of the individual abrasive particles, in the same way sandpaper grains receive classification by their size. Grit sizes range from 16 to 60, with smaller numbers indicating larger, coarser particles and larger numbers indicating smaller, finer particles.
BOND
The bond of a cutting wheel is the substance that holds the abrasive grains in place.
Manufacturers often refer to the grade, or hardness, of a wheel. The grade signifies not the hardness of the abrasive grains themselves but the hardness of the bond holding them in place. Generally, under identical conditions, a harder bond means the cutting wheel will have a longer lifespan, whereas a softer bond means the cutting wheel will have a shorter lifespan.
A softer bond does provide certain advantages - it sheds its grains more rapidly to provide a faster cut. With a stronger bond, the bond may hold the grains in place after they have become worn. A softer bond releases them faster to reveal fresh, sharp grains more often and increase the wheel's cut rate.
With certain metals, it is important not to introduce contaminants into the metal when cutting. When cutting stainless steel and aluminum, always make sure the abrasive contains less than 0.1% of chlorine, iron, and sulfur, ensuring it is contaminant-free. Contaminant-free products will have identifying labels.
One of the bonds commonly used with abrasive grains for cutting wheels is resinoid. Resinoid bonds contain organic compounds. They tend to have better shock resistance than other types of bonds and can withstand operation at elevated peripheral speeds. They are ideal for cut-off applications, and they allow for self-sharpening by exposing new grains. Some specialized bonds are resin-over-resin bonded. These bonds provide additional moisture and heat resistance, as well as a stronger overall bond to make better use of the grains.
FIBERGLASS
Cutting wheels contain fiberglass that may provide single, double, or triple reinforcement. Single reinforcement relies on a single layer of fiberglass and is useful for delivering exceptional cutting speed while reducing burrs on the workpiece. Double and triple reinforcement use multiple layers of fiberglass to provide added support for high-vibration and heavy-duty industrial applications.
