Abrasive products used for finishing of metal and non-metallic workpieces in the production plant are generally categorized into two main groups: bonded abrasives (usually grinding wheels) and coated abrasives (belts, discs, sheets, etc.). These are the products used to remove stock during the production process. But there is a third category of abrasives that serve a specialized and highly necessary function of preparing and applying the final surface finish, which can be critical to the performance and appearance of the workpiece. These are the non-woven abrasives.

These products are manufactured using a “web” of nylon fibers that are bonded together (not woven together – hence the name) with synthetic resins. The fibers are impregnated with abrasive grain, producing a cushioned, three-dimensional material that is pliable, conformable to the workpiece, and long-lasting. Non-woven abrasives can be the ideal grinding products for deburring, cleaning, and imparting the desired finish to a wide variety of materials. A basic understanding of how these products are made, and how they should be selected and used to their maximum benefit, can help the metalworking manufacturer achieve the desired surface finish.

It is often said that the job of non-woven abrasives begins where other grinding products leave off. The relatively non-aggressive nature of nylon and the abrasive grit used in non-wovens make them excellent finishing tools. With their open-mesh construction, non-wovens are waterproof, washable, and resilient. They resist loading and rusting, and are not conductive. In the standard non-woven design, abrasive grain is uniformly dispersed throughout the nylon web, providing a continuous supply of new grain as the old grain and fibers wear away during use. While 60 grit to 80 grit abrasives are considered intermediate sizes in other products, they are considered coarse for non-woven products.

Non-wovens can be used on a range of metals, including aluminum, brass, copper, nickel, chrome plate, stainless steel, and titanium, as well as other hard-to-grind materials such as ceramics, glass and plastic. Used wet or dry, non-wovens enable the user to achieve a consistent, uniform finish, and conformability to irregular surfaces, with minimal smearing and discoloration of the workpiece.

While non-wovens are made in a different way than conventional coated abrasives, both types of products use many of the same abrasive minerals. Silicon carbide is sharper, cuts faster and produces finer scratch patterns on most surfaces. Aluminum oxide is more durable and tends to last longer. It is more aggressive on certain applications (such as hardened steel parts), and produces less discoloration on aluminum. When we talk about grit, we are referring to the size of the abrasive grain impregnated into the nylon web. The lower the number, the larger the grains. Use of large particles (coarse grit) results in a more aggressive cut and a coarser finish. Small size particles result in a non-woven product that produces fine surface finish, if all other conditions are equal. In specifying a conventional bonded or coated abrasive product, the purchaser selects a specific grit size – say, 120 grit. With non-woven abrasives, by comparison, one of the following designations is used: 

Coarse (C)
Medium (M)
Fine (F)
Very Fine (VF)
Ultra Fine (UF)
Micro Fine (SF)

040 – 080
100 – 150
180 – 220
240 – 360
600
1000 – 1200

Two other factors in the design and manufacture of non-woven abrasives are the sizing of the nylon fibers and the bonding agents used. Fiber size has a significant effect on the product’s cutting characteristics, while the type of waterproof resin used to bond the fibers together (and to anchor the abrasive to the web) can alter the characteristics of the product. FibraNEX selects the appropriate fiber size and bonding agent based on the intended application for the product; therefore, these components are not included in the product offering specifications.

A typical specification on a non-woven abrasive product might look like this: 8 A/O MED. The first symbol – in this example, the “8” – refers to the product’s density. This can range from 2 (open/most conformable) to 9 (densest/ most durable).
The second symbol denotes the abrasive used. “A” or “A/O” refers to aluminum oxide, while “S” or “SC” stands for silicon carbide. The final designation – “MED” – denotes the grit size of the product, as outlined above.