For metal fabrication operations, bonded and coated abrasives are frequently used for heavy stock removal such as weld blending. While these products are ideal for rapid material removal, applications such as surface finishing, cleaning, deburring and light blending require less aggressive products.
Wire brushes and non-woven abrasives are two types of products used for surface conditioning applications requiring little or no stock removal. An understanding of how these products operate allows users to achieve maximum benefits from both.
Applications of wire brushes and non-woven abrasives frequently overlap. Both are effective tools for removing surface contamination, such as rust or heat discoloration, and both can be used in rework applications, such as removing gaskets or adhesive residue. Four major differences drive selection of one of these products over the other.
- Wire brushes do not remove base material. For applications where part dimensions are critical, wire brushes have the advantage in that they are capable of separating surface contaminants from base material without impacting part dimensions.
- Non-woven abrasives produce a bright, shiny surface finish and can be used to produce the straight-line scratch pattern required by stainless steel fabricators. In contrast, wire brushes make the work surface look like an “orange peel,” which does not have scratches.
- Wire brushes have much better edge durability than non-woven abrasives. While both can be used in many deburring applications, brushes offer better process economics due to their durability.
- Because non-woven abrasives are primarily composed of nylon, they cannot be used on hot parts, which can cause them to melt. This makes them unsuitable for applications such as cleaning hot welds.
At the end of the day, one of these driving differences usually trumps all of the others. According to Ron Vogt Jr., category manager, MRO, Weiler Abrasives Group, “In many cases, the user will select one over the other based on a critical outcome. A wire brush can’t produce a #3 finish in a stainless fab shop, and a non-woven can’t be used for weld cleaning on a pressure vessel.”
Better Or Worse
As mentioned, wire brushes have an advantage in burr removal applications due to their high edge durability. “Wire brushes are excellent tools for burr removal,” Vogt Jr. says. “They have the ability to remove the burr from the part while leaving a lightly blended edge.”
However, according to Vogt Jr., non-woven abrasives are the better choice in a variety of situations.
“In applications requiring burr removal and generous edge radiusing, non-wovens are the better alternative,” he says. “Tube deburring is usually done with wire brushes because they leave the edges very clean and ready for fit-up. Medical instruments are commonly deburred with non-wovens because they can produce a large, smooth edge radius.”
What factors drive performance attributes?
Conformability in cleaning applications: If a part geometry requires significant conformability, crimped wire brushes are hard to beat. Brush aggression can be increased by switching from a crimped wire brush to a knotted wire brush, but this comes at the cost of reduced compliance.
According to Vogt Jr., “If you need to press on a crimped wire brush to get the surface clean, try a knotted wire brush. If you need to press on a knotted wire brush to get the job done, switch to a non-woven.”
Coating removal: Applications such as removing paint and adhesive residue are ideal for wire brushes because they do not become loaded with the foreign material. The filamentary nature of brushes prevents them from becoming clogged and allows them to continue cleaning at a high rate throughout their useful life.
Achieving cosmetic surface finishes: When a user requires a bright, lustrous finish, non-woven abrasives are usually the right product for the job. Non-wovens are made with different densities for specific applications.
Metal finishing wheels have a lower density, which increases their compliance and makes them ideal for making long, straight scratches. In contrast, deburring and polishing wheels are very dense, which improves their ability to withstand the pressure of working on edges.
Optimizing process economics: If a wire brush and a non-woven abrasive can both do a specific job, wire brushes typically offer the best cost-per-part due to their excellent durability. The key to maximizing the life of a wire brush is selecting the ideal wire size.
Non-woven abrasives and wire brushes are used in a range of equipment, from machining centers and deburring machines to handheld angle grinders and benchtop grinders. The configurations are different but the basic operating principles are the same.
Grains And Fibers
Non-woven abrasive products are produced by taking a web of nylon fibers and coating it with abrasive grains using synthetic resins. As a non-woven abrasive is used, the nylon fibers wear away and fresh grains are exposed, providing a continuous supply of new, sharp cutting edges.
The density of a non-woven refers to the amount of abrasive material that is compressed into the shape and size of the non-woven product. In general, harder density products cut faster and last longer; softer density products offer more conformability and produce unique surface finishes.
Grit size refers to the size of the abrasive grains coated into the nylon web. Use of larger grains results in a more aggressive and coarser cut. Smaller grains produce a finer surface finish. Typical grit size designations for non-woven abrasives are:
- Coarse grit – 50 to 80
- Medium grit – 100 to 150
- Fine grit – 180 to 220
- Very fine grit – 240 to 360
- Micro fine grit sizes can go up 1,200
“It’s just a matter of the final finish that you want to put on the part,” Vogt Jr. says. “If you’re looking for a #3 finish on a stainless sheet, you need a different grit than if you are producing a Ra 10 microinch finish on a transmission component. Large grains do the work faster, but they leave bigger scratches behind.”
Non-woven abrasives can be used wet or dry on any metal surface. The use of lubricants, such as water, water-soluble oil and straight oil, decreases heat generation and improves surface finish.
Weiler non-woven abrasive products include convolute wheels, unitized wheels, surface conditioning discs and hand pads.
Convolute wheels come in a range of sizes and specifications for deburring, cleaning, blending, finishing and polishing applications. They are generally used on pedestal grinders or other types of fixed equipment.
The wheels are made by wrapping the non-woven web material around a center core and bonding the layers together. Because of their wrapped construction, they must always run in the direction of the arrow printed on them.
Unitized wheels are typically smaller than 6 in. in diameter and used on portable tools. Unitized wheels are formed by compressing multiple layers of non-woven web material into a block. Wheels of different diameters and thicknesses are then produced from these blocks. Because they are not produced by wrapping, unitized wheels are bi-directional.
Surface conditioning discs and belts are made by attaching the non-woven web material to a scrim backing, which gives the product sufficient strength to be used in thin configurations. These products are ideal for producing fine surface finishes with common tools such as belt sanders and angle grinders.
Hand pads are not as strong as other non-woven abrasive products but provide excellent conformability and flexibility in off-hand cleaning applications.
Wire brushes are an entirely different beast than non-woven abrasives as far as construction and configuration. For wire brushes to work efficiently, the tips of the wires must be as perpendicular as possible with the work surface. Users should select a wheel brush, cup brush or end brush based on the power tool that will be used and the goal of keeping the wire tips perpendicular to the work surface.
As mentioned, wire diameter is an important factor. Thin wires are more flexible and more resistant to breakage, but are not as aggressive. Thicker wires are stiffer and more aggressive, but also offer less durability.
“Although some of it is based on the composition of the wire, in general, coarser wire has less durability than finer wire,” Vogt Jr. says. “So, you always want to choose the finest wire diameter that will get the job done.
“For example, you would use a knotted wire wheel brush with a coarser wire, such as 0.02 in., for cleaning welds because the wire tips need a lot of energy to separate the surface contaminants from the weld,” he explains. “But to remove light heat discoloration from the corner of a welded enclosure, you may use a 0.006-in. crimped wire in an end brush.”
In conclusion, wire brushes and non-woven abrasives are great tools for applications from cleaning to surface finishing. The best way for abrasive product manufacturers to bring value to end users is to help them understand the advantages and disadvantages of each product so they can pick the right tool for the job.