Do you know the difference between a wire brush, a grinding wheel, and a flap disc? Knowing this can help ensure you are spending more time welding and less time cleaning and making repairs.
Following best practices will extend product life, ensure your safety, and increase productivity and efficiency.
It is critical to eliminate all inclusions and pollutants when preparing a material’s surface for welding and during interpass and postweld cleaning. Removing as little material as possible between weld passes saves time and money since any material removed will ultimately need to be replaced via the most expensive consumable—the filler metal. Removing too much of the base material during preweld surface preparation can also affect weld penetration, impacting the strength and integrity of the finished weld.
For these reasons, always choose the best surface preparation and cleaning tools for the job. The right solution provides efficient, effective performance—and allows you to spend more time welding and less time cleaning and making repairs.
Common Tools in Welding Applications
Three common tool categories are used for surface preparation and cleaning in welding applications:
1.Bonded abrasives/grinding wheels
2.Coated abrasives/flap discs
3.Wire brushes and wheels
What you should choose depends on the requirements of the application and, of course, your personal preference.
Abrasive products and wire brushes differ in their performance and purpose. Abrasive products are designed to remove base material, whereas wire brushes are not. When surface preparation or weld cleaning requires that you remove slag or mill scale, a wire brush is generally recommended. Note, heavy mill scale sometimes can be too much for even the most aggressive wire brush. In these instances, choose an abrasive product. Abrasive products are specifically designed for applications such as stock removal, edge beveling, chamfering, and weld grinding and blending. Conversely, if an application requires that you preserve the base material during surface preparation and weld cleaning, a wire brush is still your best choice. Here’s how these products work.
Bonded Abrasives/Grinding Wheels. A combination of the grain type, grain size, and bonding agents (resins and additive fillers) determines the performance of each. Bonded abrasives are generally more aggressive and remove material faster, requiring a skilled operator who knows how to prevent damage, gouging, and undercutting. Wheels are constructed of abrasive grains, including aluminum oxide, silicon carbide, zirconia alumina, ceramic alumina, and combinations of these grains. A resinoid (organic) bonding agent is mixed with the abrasive grains. Finally, this mix is molded and combined with fiberglass reinforcement layers for durability and strength.
Aluminum oxide (AO) wheels are the most popular and are good for many general-purpose applications. Products made with a combination of ceramic and zirconia alumina cost more, but typically provide a better overall life and material removal. They are a good choice for materials such as armored steel, structural steel, cast iron, and alloys.
Coated Abrasives/Flap Discs. These items are constructed using the same grain types as those found in bonded abrasives. Coated abrasives bond the abrasive grains to a backing cloth, which is most commonly a cotton, polyester, or blended backing rather than the hard grinding wheel found on bonded abrasives. This abrasive cloth can be cut into smaller flaps and layered radially to form a flap disc. It is this layered construction that gives flap discs a much softer, more forgiving feel.
The flaps are designed and positioned to wear away as the grains deplete, exposing new, fresh, and sharp grain underneath. Flap discs are often more comfortable to use and offer the aggressive cutting and grinding action of a grinding wheel; however, they also allow for blending and finishing work, which is important when the material needs to be painted, primed, or powder-coated.
Wire Brushes and Wheels. These are the primary choice for weld cleaning, when it is necessary to remove spatter and other contaminants prior to finish or the next weld pass. Remember, the tips of wire brushes do the work, functioning like tiny hammers hitting and preparing the work surface. Applying the appropriate pressure is critical to power brush performance, as excessive pressure flexes and bends the wires, preventing the tips from working. This can lead to premature wire breakage and dramatically reduce brush life.
The right surface preparation and cleaning tools provide efficient, effective performance and help ensure you spend more time welding and less time cleaning and making repairs.
Power brushes provide the speed and efficiency necessary to complete cleaning and surface preparation applications quickly and efficiently. When you are removing coating from a surface, such as epoxy, paint, or rubber, coated abrasives have a tendency to load—in other words, the material being removed packs between the grains and builds up—stopping their ability to perform. A power brush’s ability to “self-clean” makes it the best choice for these cleaning applications.
When choosing a power brush, you have several knot styles, wire gauges, and trim length options. By changing one or more of these characteristics, you can fine-tune brush performance for a specific application. For example, stringer bead brushes have narrower knots twisted from base to tip, making them better suited to penetrate tighter spaces like corners, fillets, and root pass welds. Cable-twist brushes are also twisted to the tips but have a wider profile that can quickly cover more surface area for fill passes. Standard twist brushes flare at the end, providing an even wider footprint as well as additional conformability.
Crimped-wire brushes provide less aggression and more conformability, making them a great choice for paint and rust removal and deburring. Crimped-wire brushes also leave a consistent “orange peel” finish, so they are a good choice for surface preparation and paint adhesion.
Wheel brushes are designed to work perpendicular to the work surface and are best-suited to smaller, tighter surface areas. Cup brushes are perfect for covering larger, wider surface areas because of their ability to clean a larger area in a single pass.
Making the Right Choice for You
When choosing a product for surface preparation and weld cleaning, consider the base material. Generally speaking, choose a carbon steel brush to clean carbon and mild steels and a stainless brush for stainless, aluminum, and exotic metals. Brushes are also available in copper and brass to prevent spark, when necessary.
Next, consider the application’s finish requirements. Is there a need to remove base material, or is the material being prepped and cleaned for finish or coating? For weld cleaning, a knot brush—stringer bead or cable-twist—is typically the best choice. When selecting a power brush, start by choosing the least aggressive option for the job.
For a coated or bonded abrasive, aluminum oxide provides the most cost-effective option for general-purpose grinding. Harder, more durable grains like zirconia alumina and ceramic maintain sharpness and resist heat, making them a much better choice for more aggressive grinding applications.
Finally, consider the size and orientation of the material to be cleaned. Cleaning the fill pass of a weld requires a very different tool than cleaning a large, flat surface. For example, a cup brush has a significantly larger footprint and, therefore, can cover a large area.
Best Practices to Maximize Performance
To achieve safe, optimal performance of any wire or abrasive product, think S.P.O.T.
S—Speed and Size. Choose an appropriately sized product for the tool, and use the manufacturer’s recommended guard. Be sure the maximum safe RPM marked on the wire or abrasive wheel is greater than or equal to the maximum operating RPM on the tool. When selecting high-performance ceramic abrasives, pay attention to tool speed. Tools with lower power can’t maintain the required speed and therefore don’t provide the full advantages of these high-performance, higher-priced products.
Knowing available product options and understanding their intended uses are important parts of getting the best results from abrasives and wire brushes.
P—Pressure. When operating wire brushes, you shouldn’t have to push harder because the tips should be doing the work. Applying excessive pressure to the brush prevents the tips from hitting the surface, so the sides of the wire begin “wiping” the surface. This reduces cleaning action and increases wire loss because of stress. If a power brush is not performing to expectation, consider changing the knot, increasing the wire gauge, or shortening the trim length. A common complaint about wire brushes is wire loss, and the main cause, in many cases, is improper use or excessive pressure.
When you are using an abrasive, increasing pressure slows tool speed and significantly increases friction and heat. Heat and pressure are the enemies of any abrasive product. Use even, consistent pressure and motion to minimize heat discoloration and maximize performance.
O—Orientation. Wheel brushes are designed for use perpendicular to the work surface. This positions the wire tips for optimum performance and reduces lateral stress on the wire, preventing wire loss, poor performance, and short brush life. Bonded abrasive cutting wheels are also designed for use perpendicular (90 degrees) to the work surface for best performance and longevity.
Grinding wheels and flap discs are designed for use at 5 to 35 degrees in general. When selecting a flap disc, choose Type 27 for finishing and applications that require lower grinding angles—5 to 15 degrees. Choose Type 29 for more aggressive, higher angle grinding—15 to 35 degrees.
T—Time. All products are designed to be moved across the work surface. When you are using an abrasive product, do not dwell in one spot as it will lead to pitting, gouging, increased heat, and reduced surface finish.
Knowing what your product options are and understanding their intended uses are important parts of getting the best results from abrasives and wire brushes. Always follow best practices to extend product life, improve operator safety, and increase productivity and efficiency. Doing so can help you complete jobs faster, saving time and money for a better bottom line.
No matter the tool, inspect the abrasive or wire brush each time it’s used for any signs of damage or wear. Replace as necessary.