GUIDE TO GRINDING WHEELS

What is a grinding wheel? Grinding wheels contain abrasive grains and layers of fiberglass bonded into a wheel shape by another substance. The abrasive grains act as grinding tools, removing material from a workpiece to shape and refine it. Grinding wheels are useful in many grinding and machining operations.

Several types of grinding wheels are available, so when a facility is choosing a wheel, it's essential to consider the specifications of contrasting styles and how well they can handle different environments and operational challenges. In this guide to grinding wheels, we discuss a few grinding wheel types, as well as their materials, design and benefits for specific applications.

TYPES OF GRINDING WHEELS

Grinding wheels — along with other more portable grinding products like cones and plugs — come in various styles. Selecting the right type of wheel for a given application allows users to get demanding metal fabrication jobs done quickly and accurately.

There are three main types of grinding wheels, where various numbers differentiate between wheels with specific properties and uses — type 1 snagging wheels, type 27 grinding wheels and type 28 grinding wheels.

TYPE 1

A type 1 snagging wheel has a straight profile and a relatively small diameter of about 2 to 4 inches. Its size makes it ideal for use on high-speed die grinders for grinding off excess metal. Weiler Abrasives' type 1 snagging wheels incorporate aluminum oxide grains for a long life grinding and a consistent cut-rate.

TYPE 27

Type 27 is by far the most common abrasive grinding wheel. Type 27 grinding wheels differ from other wheels in that they have a flat profile with a depressed center. A depressed center allows for clearance when the operator must work at a constrained angle.

Using a wheel with a depressed center allows for a range of grinding angles, typically from 0 to 45 degrees. However, the optimal angles for working with type 27 grinding wheels range from 25 to 30 degrees. The steeper the grinding angle, the more aggressive the cut will be.

Working at shallow angles with these wheels requires some consideration of potential ramifications. Grinding at shallow angles can prolong the wheel's lifespan, but it also often compromises the cut-rate. On harder materials, shallow grinding angles may also increase unwanted vibration and chatter.

TYPE 28

Type 28 grinding wheels, also known as saucer wheels, have similarly depressed centers and are optimized for low grinding angles. They differ from type 27 wheels in that their concave or saucer-shaped design allows for better access to the workpiece — especially in tighter areas, such as corners, fillets and overhangs — and increased aggression at smaller working angles. They can work at angles between 0 and 30 degrees but typically work best for use with grinding angles from 0 to 15 degrees.

GRINDING WHEEL MATERIALS

The materials in each grinding wheel break down into a few main components — the grains, the bond and the fiberglass that reinforces the wheels to give them strength and stability for use in demanding applications. The grit of the wheel is also an essential element that helps determine performance.

GRAINS AND GRAIN BLENDS

The abrasive grains provide the essential functionality of a grinding wheel because they remove material from the workpiece. A few commonly used grinding wheel abrasives are ceramic alumina, zirconia alumina, aluminum oxide, white aluminum oxide, aluminum oxide and silicon carbide. Grains can be blended together to achieve different performance characteristics as well.

Ceramic alumina: These grains offer the benefit of self-sharpening and micro-fracturing crystals. They are relatively cool when in use, and they provide the longest operating life under moderate to high pressure. They grind at lower temperatures and generate less friction — one main benefit of these qualities is that they minimize heat discoloration on the workpiece. Ceramic alumina is ideal for hard-to-grind metals such as armored steel, titanium, hard nickel alloys, Inconel^®, tool steel and stainless steel.
Zirconia alumina: Zirconia alumina grains provide a fast cut and a long life on metal workpieces. They are self-sharpening and deliver rapid, consistent grinding, especially on metals like steel and stainless steel. They also hold up well under high pressures and extreme temperatures.
Zirconia alumina blended with ceramic alumina: If you like the performance of a zirconia alumina grinding wheel but are looking for an extra boost a blend with ceramic alumina will deliver faster cutting with less effort.
White aluminum oxide: White aluminum oxide grinding wheels offer a relatively fast cut-rate and an extensive lifespan. They are ideal for grinding stainless steel and harder-grade steel.
Aluminum oxide: An aluminum oxide grain is ideal for steel, iron and other metals. Although it is hard and durable and provides a sharp, fast initial cut, the grain dulls over time and lacks the cut-rate and potential longevity of some other grains. Aluminum oxide provides exceptional value and cost-effectiveness while still offering the excellent quality and consistent performance necessary in a grinding wheel.
Silicon carbide: Silicon carbide is an extremely hard grain that is very sharp and fast cutting but friable, not as tough as other grains.
Silicon carbide/aluminum oxide blend: A wheel made from a blend of silicon carbide and aluminum oxide provides ideal grinding for aluminum and other soft alloys. These grains offer extended life spans and fast, consistent cut rates on aluminum and other soft metals.

Grains also come in various sizes — the size of a grain refers to the size of the individual abrasive particles, similar to the grades for sandpaper particles.

BONDS

The bond is the substance that causes the abrasive grains to adhere to the wheel. Bonds can consist of different materials. Common materials include shellac, resinoids, rubber and glass or glass-ceramic. At Weiler Abrasives, our portable grinding wheels contain resinoid bonds.

The bond on a grinding wheel may be either hard or soft. A harder bond extends the wheel's lifespan, provided the user operates and maintains the wheel correctly. A softer bond, on the other hand, allows for smoother grinding and exposes new grains more quickly. Choosing the correct bond for a given application can help balance performance and longevity. The type of metal can also influence the bond that's best for your application.

A grinding wheel's bond sometimes contains iron, sulfur and chlorine, which can pose challenges if they adhere to the workpiece during grinding. Weiler Abrasives offers several wheels that minimize these elements. Our Tiger^® Ceramic, Aluminum, and INOX wheels are contaminant-free, containing less than 0.1% chlorine, sulfur and iron. They help prevent corrosion on stainless steel and aluminum workpieces.

The bond on a grinding wheel helps provide a consistent cut rate by exposing new grains over time. As older grains become worn, the grain particles fracture as they are designed to — thereby exposing new abrasive surfaces, leaving fresh abrasive particles exposed in their places. Ideally, the composition of the binding is such that under normal working conditions, wear and tear will remove worn abrasive particles and leave fresh ones in place, maintaining the wheel's superior cut-rate and performance.

The abrasive particles bound to the wheel also have a characteristic known as grade. Grade refers to hardness, but not the hardness of the particles themselves — it refers instead to the strength of the bond holding the particles to the wheel. A wheel with a stronger bond typically has a longer life. A softer bond is designed to break down faster to maintain a consistent cut rate as new sharp grains take the place of worn ones. The letters N, R, S and T specify the hardness of a bond, with the letters that come later in the alphabet referring to harder bonds. As a general rule, a wheel with a softer bond will perform better on a hard metal, while a hard bond will perform better on a softer metal.

FIBERGLASS

The fiberglass structure and design on a grinding wheel provides reinforcement, rigidity and superior grinding ability. All Weiler grinding wheels come with triple-reinforced fiberglass that gives additional support and strength for aggressive stock removal. Our Tiger brand of performance grinding wheels has the outer layout of fiberglass cut back to allow for aggressive grinding from the outset with no break-in period.

GRIT

The grit of a wheel is critical for supplying the right abrasion. Grit measurements generally range from coarse to fine. On Weiler Abrasives' grinding wheels, the coarsest grit has a rating of about 24 and the finest grit — the grit on snagging wheels — has a rating of about 36. Selecting the right grit level for a particular application helps ensure sufficient grinding power. A course grit has a better removal rate, while a finer grit requires less pressure during application and allows for a better final finish on the workpiece.

SELECTING THE RIGHT SIZE GRINDING WHEEL

When selecting a grinding wheel, users should consider two primary factors — diameter and thickness. Both metrics affect the wheel's usability and performance.

DIAMETER

The choice of diameter for a grinding wheel generally depends on the available tool. The primary reason for fitting the grinding wheel diameter to the tool is safety — the operation of the tool should never exceed the RPM rating on the abrasive. Smaller power tools tend to operate at higher RPM than larger power tools, and the design of abrasives and brushes enables them to meet the same standards. Running a wheel with only an 8,500 RPM rating on a grinder that operates at 13,000 RPM could cause the abrasive to fail and injure the operator.

Choosing the correct diameter also enhances safety because it allows for the use of proper guards. Trying to fit a 6-inch abrasive on a 4.5-inch grinder necessitates removing the protective guards, and running the grinder without guards would increase the operator's chance of injury if the abrasive failed.

Product life is an additional factor in the choice of grinding wheel diameter. Larger-diameter wheels last longer. Especially in applications where the operator must run the grinding wheel for a sustained period, using a larger-diameter wheel can improve productivity by reducing the number of times the operator must stop and replace the abrasive.

The configuration of the workspace and workpiece also influence the choice of diameter. For instance, an operator working in a cramped space or on a tricky area of the workpiece may choose a die grinder with a small 3-inch wheel for better access.

THICKNESS

The thickness of a grinding wheel impacts its performance and wheel life. Our grinding wheels typically come with a quarter-inch thickness. This measurement gives our wheels a superior balance of precision, wheel life, and cut-rate when grinding.

Combination grinding and cutting wheels with 1/8-inch thickness are also available. These wheels allow for grinding and for making cuts that require a thinner wheel. The benefit of these thinner combo wheels is that they enable the operator to perform both 90-degree cuts and shallow-angled grinding without having to change the abrasive used on the wheel.

GRINDING WHEEL APPLICATIONS

Thus far, we've discussed how different wheel types and compositions can influence the performance of a grinding wheel. And we've explored how selecting particular wheel diameters and thicknesses can optimize grinding wheels for specialized applications.

Now let's examine a few particular applications that require the use of grinding wheels and consider the optimal wheel specifications for each.

Multipass welding work: For work on pipelines, pressure vessels, and other critical to quality welding operations, operators will likely want a wheel such as the Tiger Zirc pipeline grinding wheel. This wheel incorporates ceramic-infused zirconia alumina with a 1/8th-inch thickness for precision and control when grinding the weld bead in a bevel. This wheel offers diameters ranging from 4 1/2 to 9 inches.
Mechanized pipe welding: For mechanized pipe welding, operators generally need thinner wheels that allow them to grind the bead without expanding or marring the bevel. The Tiger Mech wheel is an ideal solution, designed for grinding starts and stops on J and K bevels. This wheel incorporates ceramic-infused zirconia alumina and a thin 3/32-inch thickness that allows for precision and consistency. The 4 1/2-inch to 7-inch diameters allow for several grinder size options when notching mechanized pipe welds.

PARTNER WITH WEILER ABRASIVES FOR SUPERIOR GRINDING WHEELS

To see the benefits of high-quality surface conditioning solutions in your workplace, make Weiler Abrasives your trusted source for portable grinding wheels. We are here to help with all your grinding challenges by providing the expertise to help you select the best abrasive grinding wheel to meet your unique surface conditioning requirements.

We also set ourselves apart from our competitors with our Value Package, offering safety training for safe and proper wheel use and direct field support that helps you solve your operational challenges and get the most productivity and profit out of your grinding wheel.