Guide to Cutting Wheels

In metal fabrication and manufacturing operations, various tools use cutting wheels to cut material from a workpiece.

What is a cutting wheel? Cutting wheels, or cut-off wheels, differ from grinding wheels in their function and structure. Where grinding wheels use an abrasive to grind large pieces of material off a workpiece from a shallow angle, cutting wheels typically make narrow, precise cuts at 90-degree angles. Consequently, cutting wheels are often thinner than grinding wheels — though they do not have the lateral strength required for side grinding, their minimal thickness makes them better for clean, accurate cuts.

Weiler Abrasives offers several cutting wheels for different applications. They provide everything from 1-millimeter cutting wheels to extended-diameter wheels for larger cuts. This guide to cutting wheels covers the differences between various types of cutting wheels and explains how to choose the right wheel for a given application.

TYPES OF CUTTING WHEELS

Cutting wheels come in a few different types. Some common types are type 1, type 27, type 41, and type 42, where the various numbers signify the wheels' different shapes and properties.

TYPE 1 CUTTING WHEEL (TYPE 41 CUTTING WHEEL)

A type 1 cut-off wheel, also known as a type 41 cut-off wheel, is completely flat. It is typically considered the most efficient type of wheel for general all-purpose cutting. Because it lacks a depressed center, it provides more cutting surface and minimizes interference with the workpiece.

The flat profile helps create deep 90-degree cuts into a workpiece. It allows for the maximum depth of a 90-degree cut at the expense of a small amount of visibility for the operator. Though their straight profile and the way they mount close to the guard can diminish visibility for the operator, type 1 cutting wheels are exceptionally useful in grinders, die grinders, high-speed saws, stationary saws, and chop saws.

TYPE 27 CUTTING WHEEL (TYPE 42 CUTTING WHEEL)

Instead of being completely flat, a type 27 cut-off wheel, also known as a type 42 cut-off wheel, has a depressed center. The depressed center allows for added clearance when the operator is working at a constrained angle, though it gives the wheel limited cutting ability when working around corners, profiles, or extrusions. The depressed shape allows for a raised hub as well to hold the wheel securely in place.

The profile of a depressed-center cutting wheel gives the operator a better view of the cut, and it provides the ability to flush-cut because the raised hub means the locking nut can be recessed. Type 27 cutting wheels are designed for right angle grinders.

CUTTING WHEEL MATERIALS

Cutting wheels typically contain a few different materials — primarily the grains that do the cutting, the bonds that hold the grains in place, and the fiberglass that reinforces the wheels.

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. 

At Weiler Abrasives, all their cutting wheels for right angle and die grinders have two layers of reinforcement. They do offer some single-reinforcement wheels in their large-diameter chop saw line and some triple-reinforced wheels in their new high-speed gas and electric saw wheel line.

SELECTING CUTTING WHEEL SIZE

With cutting wheels, the tool the operator has access to will often determine the wheel size, and selecting the correct size for the given application is also essential. Choosing the correct size involves calculating the right rate of revolutions per minute (RPMs) — the RPM rating of the cutting wheel should match or exceed the RPM rating on the grinder that will use it. In addition to verifying the RPM rating, it is also important to ensure that the wheel fits on the tool without interfering with or removing the guard.

CUTTING WHEEL DIAMETER

A wheel's RPM rating tends to correspond with its diameter and the tool it is designed for. Common cutting wheel diameters range from 2 to 4 inches for die grinders, 4 to 9 inches for angle grinders, and 12 to 20 inches for chop, stationary, or high-speed saws.

CUTTING WHEEL THICKNESS

The right wheel thickness often depends on the precision and accuracy necessary for the cut. For a highly precise cut, a thinner wheel can perform with greater accuracy and precision. They cut more quickly and generate less heat. Thinner wheels also remove less material with each cut, which is ideal when making repairs or fitting up parts. The tradeoff is that they tend not to last as long as thicker wheels under identical conditions. In applications where precision and accuracy are not as critical but longevity is, a thicker wheel may be suitable.

Weiler Abrasives offers two ultra-thin high-performance cutting wheels — the Tiger® Zirc Ultracut 1-millimeter and the Tiger Inox Ultracut 1-millimeter. Both of these cutting wheels come in 4 1/2- or 5-inch diameters. The Tiger Zirc Ultracut 1-millimeter offers an ultra-fast cutting rate and long life, and it is ideal for cutting thin sheet metal, tubes, profiles, and small cross-section rods. The Tiger Inox Ultracut 1-millimeter is ideal for stainless steel because it is contaminant-free.

Weiler Abrasives has an exciting new line of chop, stationary, and high-speed saw wheels as well. The chop saw wheels have a 3/32-inch thickness, and the high-speed saw wheels and stationary saw wheels have a 1/8-inch thickness. These cutting wheels are ideal for cutting applications in the metal fabrication, construction, and rail industries, and some of the specialized models can provide precise rail cutting, burr-free cutting, and stud cutting for heavy-duty applications.

CUTTING WHEEL APPLICATIONS

So far, we've discussed how types 1, 27, 41, and 42 cutting wheels offer distinctive shapes for different cutting applications. We've delved into the various common grains used in cutting wheels and how they are optimized for use on different metals, and we've explored the way diameter and thickness affect wheel speed and precision. Now let's look into a few applications for industrial and professional cutting wheels and how to choose the right wheels for these uses.

1. GENERAL FABRICATION

In general metal fabrication, 0.045-inch wheel diameters are common choices. With thinner materials, an operator may want to choose a 1-millimeter wheel instead for greater precision, less heat generation, and fewer burrs that will require removal before welding. The choice of grain will likely depend on the material composition of the workpiece — higher-performing grains for structural steel and difficult-to-cut metals, contaminant-free wheels for stainless steel.

2. PIPE FABRICATION

In metal pipe fabrication, the choice of cutting wheel often depends on the diameter of the pipe to be cut. For a 3/4-inch or smaller pipe, a 4 1/2-inch diameter will usually be sufficient. For a pipe of up to 2 1/2 inches, a 6-inch cutting wheel is effective, and for a pipe of up to 3 1/2 inches, a 9-inch cutting wheel is often most suitable. It's also advisable to choose the thinnest wheel possible to minimize heat and friction and to use a type 1 wheel for a deeper cut unless the application imposes a particular constraint. For larger pipe often found on the pipeline, a depressed-center cutting wheel provides added clearance when working at a constrained angle, and 0.045-inch wheel thickness is ideal for cutting applications in fabrication yards or on the right of way for field repairs.

3. SHIPBUILDING

When an operator is working on the confined, hard-to-access spaces of a ship, making a cutting wheel last as long as possible is often a priority. For this reason, the operator will often want to choose a harder, potentially longer-lasting wheel like Tiger Ceramic. However, when operators must use air tools whose hoses have stretched over long distances to access difficult areas of the ship, the tools may be underpowered. In this case, wheels with a soft bond will be ideal because they make it easier to maintain a fast cut. In shipbuilding, the work material often influences the cutting wheel selection. When working with aluminum, an operator may want to select a cutting wheel that will not load or gum up, like Tiger Aluminum.

4. WELDING PREPARATION

Preparing for welding typically involves exact metal cutting. With a basic cut-off operation, precision is not critical, but with complex work or repairs that need to preserve the initial aesthetic qualities of the material, precision can save time and money. Using a 0.045-inch cutting wheel — a little more than a millimeter thick — is common in welding to allow for precise and accurate cuts. For precise cuts on thin sheet metal, profiles, and small diameter rods, a 1-millimeter UltraCut wheel will provide smooth cutting and exceptional control for clean, ultra-precise cuts.

5. RAILWAYS 

Modern railways use hard-to-cut alloy steels, so a high-performance cutting wheel is necessary for high-speed gas saws. A self-sharpening zirconia alumina grain that retains a high cutting performance throughout the life of the wheel offers excellent performance. The Tiger Zirc 14- and 16-inch cutting wheels are designed specifically for high-speed gas saws and deliver the high-performance solutions needed to increase productivity and profitability.

6. CONSTRUCTION

Building and construction sites feature a wide variety of metal cutting applications. Operators often look for a wheel that can do it all, from cutting off rebar to making long cuts on sheet metal. Many times, an aluminum oxide wheel provides the right mix of versatility, performance, and price. The Tiger AO line offers both flat and depressed-center cutting wheels in various sizes for die and right angle grinders. The Tiger AO line also expands into larger sizes from 12 to 16 inches for chop saws and high-speed gas and electric saws.

These large-diameter cutting wheels have several signature wheels designed with the construction industry in mind. For chop saws, the line includes a wheel designed for stud cutting and options for burr-free cutting that feature a single layer of fiberglass. The high-speed saw offering includes wheels with three layers of fiberglass for added support in heavy-duty cutting applications.

Previously Featured on Weiler's blog.