Getting to Know Cut-Off and Grinding Wheels (Type 1 Cut-Off Wheels and Type 27 Grinding Wheels)

What are grinding wheels? Grinding wheels are bonded abrasive wheels that are designed to cut or grind steel and other materials. They contain specially sized abrasive grain and layers of fiberglass reinforcement sheet pressed into a wheel form then baked at high temperatures. Grinding wheels are used on a wide range of tools, including right angle grinders and cut-off saws.

ABRASIVE GRAIN

The hard and tough abrasive grains grind different types of materials. Each grinding wheel is made to cut or grind specific materials. It is important to choose the right tool for the job.

Abrasive grain on grinding wheels can vary in size and type and can also be combined for matching the cutting properties to the application. Abrasive grains fracture during use which constantly exposes newer, sharper edges. The way a specific grain fractures is important to maximize productivity, minimize overheating or increase the life of the abrasive product. The main abrasive grains used in bonded abrasive wheels are listed below.

• Ceramic alumina: Micro-fracturing creates an abrasive wheel that is self-sharpening. Micro-fracturing ensures relatively cool temperatures during use. Products using ceramic alumina have a superior life comparison to other abrasive products. Since lower temperatures are maintained during grinding, the result is minimal heat discoloration. Use ceramic alumina on tool steel, stainless steel, armored steel, titanium, hard nickel alloys, Inconel®, and other hard-to-grind metals.
• Alumina Zirconia: When working with metal, you need a fast cut and long blade life. Alumina zirconia is tough, hard, and self-sharpening. The result is consistent, productive cutting, especially on steel and stainless steel. This grain is well known for holding up under extreme temperatures and high pressures.
• Alumina zirconia blended with ceramic alumina: The result of this combination is faster cutting but with less effort.
• White aluminum oxide: White aluminum oxide is a friable specialty grinding material. It fractures at lower pressures at lower temperatures. It is used for specialty applications such as die grinding and for use on tungsten carbide, brass, and non-ferrous metals.
• Aluminum oxide: For cutting steel and other ferrous metals use a cut-off wheel made with brown aluminum oxide. This general-purpose abrasive grain is hard, tough, and durable for a sharp, fast initial cut and holds up to higher pressure applications. It takes higher pressures to fracture aluminum oxide than it does other grains. Compared with premium abrasives, A/O bonded abrasive wheels will get the job done but may not last as long as wheels made with premium abrasives. Bonded abrasive wheels with brown aluminum oxide offer value and cost-effectiveness combined with quality and consistent performance.
• Silicon carbide: At nearly the hardness of diamond, silicon carbide is very hard and sharp. It is used for fast cutting of stone, concrete, block, brick, and asphalt. It is not as tough as other grains due to its friability, but it is the right mineral for the previously mentioned applications. It is often used to cut soft, non-ferrous metals such as aluminum, copper, and brass. It is also used to cut PVC pipe quickly.
• Silicon carbide/aluminum oxide blend: Formulated specifically for extended life and fast, consistent cut rates on ductile iron. The blend of aluminum oxide and silicon carbide will give you the best results in this tough application. This blend is a balance between the hardness of silicon carbide and the toughness of aluminum oxide. It is often the choice for use on PVC water pipes.

BONDS

The bond is the substance that binds the abrasive grain and the fiberglass reinforcement together. Material used for the bond is typically resinoid (phenolic resin). Phenolic resin provides a strong bond that withstands the high heat of grinding and cutting. Virginia Abrasives’ bonded wheels use a resinoid bond. For specialized applications, there are a wide range of bonds. Bonds can range from shellac, resinoid, rubber, or glass, glass-ceramic (vitrified)

The bond can range from hard to soft. A harder bond increases the life of the product, with correct operation and maintenance. A softer bond wears away and exposes new abrasive grains more quickly It allows for consistent cutting of hard materials. When you choose the grinding wheel, you need to consider the properties of material that is being cut to match with performance of the wheel.

The grinding wheel’s bond provides a consistent cut rate by exposing new grains over time. The grain particles fracture as they become worn, which is what they are designed to do. This process exposes new abrasive surfaces, and the duller particles worn away in the grinding process. Fracturing of abrasive particles maintains the wheel’s cut-rate and performance.

GRINDING WHEEL TYPES

Virginia Abrasives offers two types of grinding wheels, Type 1 and Type 27:

• Type 1 cut-off wheels are flat and thin. They are perfect for use on high-speed cut-off saws for cutting metal or concrete. Virginia Abrasives Type 1 grinding wheels feature aluminum oxide or silicon carbide abrasive grains, to provide optimum performance, life, and consistent cut rates. Type 1 wheels are specifically designed for cutting. Side grinding on a Type 1 wheel is forbidden and dangerous.
• Type 27 grinding wheels differ from Type 1 in that they have a depressed center that allows for clearance when the operator must work at an angle, usually from 0 to 45 degrees, but the optimal angle for a Type 27 grinding wheel is 25 to 30 degrees. Type 27 wheels are used for surface, edge grinding and surface contouring.

VIRGINIA ABRASIVES’ CUT-OFF AND GRINDING WHEEL TYPES

We carry four types of grinding and cut-off wheels based on the material they are designed to cut; Metal, Concrete, Asphalt and Ductile.

• Virginia Abrasives’ METAL cutting wheels are composed of aluminum oxide abrasive grain and use a medium hard resinoid bond material for superior performance.
• Our CONCRETE cutting wheels are composed of silicon carbide abrasive grains and employ a medium-hard resinoid bond to increase the abrasive performance on the concrete surface.
• ASPHALT Blades are composed of a blend of silicon carbide and aluminum oxide with a hard resinoid bond to resist the abrasive nature of asphalt.
• DUCTILE Blades are composed of a blend of aluminum oxide and silicon carbide with a medium-hard resinoid bond.

All grinding wheels are marked with recommended applications and warnings for safe use. Be sure to read and follow the instructions. Please see our Safety Dos and Don'ts While Working with Cut-Off and Grinding Wheels