Abrasives are excellent tools for cutting, smoothing, polishing, and finishing various workpieces. Without them, all the work they do would need to be done by hand.
Choosing the right abrasive for the job can be challenging, but this article will help readers make informed decisions. The post explores the various types of abrasives and the applications in which they perform best. By understanding the differences between bonded, coated, and non-woven abrasives, readers will be able to make informed choices about which type of abrasive to use in different situations. Whether you are a professional or a DIY enthusiast, this post is a must-read for anyone looking to improve their results.
The following is a summary of each type of abrasive, when to use it, and when each is not the best choice open to you.
Bonded Abrasives
Bonded abrasives use a mix of abrasive grain, filler, and bonding agents to remove stock, grind materials, blend welds, cut, bevel, and sharpen materials, and create precision finishes. Grits available run from extremely coarse up to ultra-fine. Many products use bonded abrasives, including, but not limited to:
- Cones
- Mounted Points
- Chop saw blades
- Plugs
- Grinding discs
- Hand held grinders
- Cut-off wheels
How Bonded Abrasives Are Made
To help bond the raw materials, several different ingredients can be used as stand-alone bonding agents and in combination with other bonding agents. Those most commonly used bonding materials include:
- Resin
- Rubber
- Glue
There are several grains available for bonded abrasives. Those include:
- cBN
- Silicon Carbide
- Diamonds
- Ceramics
- Aluminum Oxide
- Zirconia
- Combinations of grain materials
In some cases, specialty abrasive formulations address specific challenges, such as grinding wheels for aluminum.
A backing sheet has adhesive applied to it, and then the grain is added. Once the adhesive sets, the abrasive sheets get cut into different sizes, shapes, and applications. The new product is used in multiple applications to help finish various workpieces.
How Bonded Abrasives Work
Softer bonds, known as “fast cuts,” quickly wear away surface grains. Harder bonds, called “long-life,” are more durable. Stainless steel applications can be worked on with contamination-free abrasives (including contamination-free bonds.)
As the abrasive works, the surface of a working material is worn or cut away. This process continues until the abrasive has worn away the optimum amount of material on the workpiece, creating a piece that is contoured and smoothed.
Benefits and Limitations
Bonded abrasives work well with specific tools because of their design and engineering. If you try to use a bonded abrasive on tools engineered for coated abrasives, you may run into issues, such as the bonded abrasive backing coming apart. However, if used as intended, bonded abrasives have very few drawbacks.
Regarding limitations, besides equipment being engineered specifically for types of abrasives, bonded abrasives are usually not very good at prep work, particularly final prep work before a finish is applied.
Additionally, the shape of many bonded abrasives products is not conducive to providing blanket coverage of an object. If the object has dips or bends, the rigid surface of most bonded abrasive products will not get into them.
Coated Abrasives
As the name implies, coated abrasives get covered with a top-coating of resin to lock in adhesive-secured abrasive particles. The “coated” part of coated abrasives refers to the method of bonding the abrasive to a product’s backing. Specifically, the resin is a protective coating that provides stability, sturdiness, and protection to the finished product.
You can use coated abrasives with multiple products. Each version of the coated abrasive comes from the manufacturer in a jumbo roll. That roll is then run through cutting machinery that produces abrasive products for:
- Sanding belts
- Spiral Bands
- Cartridge rolls
- Drums
- Abrasive sheets (sandpaper)
- Quick change discs
- Flap discs
- Sanding discs
- Sanding rolls
- PSA sanding discs
For example, some coatings provide heat resistance protection to avoid heat damage to the abrasive. A special coating is also applied to prevent stearate buildup, and another serves an anti-static function. Each coating must dry first before any manipulation of the abrasive is possible.
How Coated Abrasives Are Made
A coated abrasive backing can be any material that is flexible and will take adhesive. That includes paper, vulcanized rubber, film, cotton, or polyester cloth. Using the backing as the base, abrasive is to the base.
A base coat of adhesive, usually resin, is applied to the backing. Once that has set (but not dried,) an abrasive product, or grain, is applied to the base coat electrostatically. The electrostatic method is used to ensure a wide and even spread of abrasive across the backing and that the grain (abrasive) is facing the proper direction.
Once the adhesive has dried, the abrasives get affixed to the backing, the resin coat gets applied over the abrasives. Dried resin locks the abrasives in place and provides some protection against wear and tear.
Coated Abrasive Grains
Multiple materials get used as grains on a coated adhesive. While there are general-purpose adhesives, most coated adhesives have a specific application. In some cases, the grains used are specialty abrasives designed to address various types of work material.
Common grains used include, but are not limited to:
- Silicon carbide
- Aluminum Oxide
- Ceramic
- Zirconia
- Diamonds (used for specialized applications)
How Coated Abrasives Work
Abrasives come in various grit sizes. The grit size determines the job the abrasive is best suited to perform. For example, larger grit sizes (24 to 60) work best on stock removal. Larger grit sizes are also ideal for deburring.
Grits ranging from 80 to 220 get used on jobs like blending, graining, and surface preparation. Ultra-fine grits, ranging from 280 through 3000, are used on smooth surfaces or as a pre-polish smoothing agent.
Benefits and Limitations
As with bonded abrasives, the benefits are that when used as directed, coated abrasives work exceptionally well. Even novices can quickly master using one for simple jobs. Coated abrasives run into the same limitations as bonded abrasives as well. Additionally, the specialty-coated abrasives provide an immediate benefit to the operator.
For example, having an extra coat to help thwart wear and tear means a coated abrasive product will last longer. That means savings in materials for the operator. The same applies to specialty abrasives that prevent stearate buildup.
The most notable drawback is that most coated abrasives do not perform the gentler work of non-woven abrasives, though some are designed for that purpose. Lacking that sensitive touch can be a major obstacle when a workpiece demands a precision finish. Coated abrasives tend to eat into their work, and controlling the depth and extent of their penetration can be a cumbersome task.
Non-Woven Abrasives
Non-woven abrasives are generally used pre-finish as a prepping agent. By preparing a workpiece for a final finish, the chances of that finish adhering and setting properly are greatly enhanced. Additionally, removing irregular points and surfaces can help avoid gaps in finish coverage and pooling of finish.
For work on prepping workpieces for finishing, non-woven abrasives can be used on metals such as aluminum, nickel, chrome, and copper. While the application of the product demands precision and care, non-woven abrasives also work very well on stainless steel and titanium. Nonmetal applications for non-woven adhesives include ceramics, plastic, and glass.
Products that non-woven abrasives are used on include, but are not limited to:
Each product can use different grit sizes, depending on the task at hand.
How Non-Woven Abrasives Are Made
A non-woven abrasive is manufactured by bonding a “web” of nylon strands via synthetic resins. The non-woven part of the name is because the bonding agent creates the web as opposed to weaving the strands together. Once the web gets formed, the fibers get treated with an abrasive grain, which provides the grinding power of the web.
Because the abrasive adheres to a non-woven web, the mass of nylon and abrasives are pliable. The flexibility of the nylons allows them to get into crevices and compensate for uneven surfaces. A benefit of this abrasive is that the entire surface of a workpiece is covered.
How Non-Woven Abrasives Work
An industry saying is that the role of a non-woven abrasive starts when other abrasives complete their jobs. Because the abrasive sits on a pliable backing (the web,) it can be used as a finishing touch in preparing a workpiece without damaging the surface of the piece and for polishing workpieces before finishing.
Additionally, the open-mesh structure is waterproof and washable.
Non-woven abrasives are not conductive, and because the abrasive is distributed evenly throughout the nylon web, new fibers take the place of old fibers seamlessly.
Benefits and Limitations
Non-woven abrasives are excellent at uneven surfaces or surfaces that are ready for a finish to be applied. Using them earlier in the grinding process not only does not accomplish the job as well as bonded or coated abrasives, but it also creates more wear and tear on the non-woven abrasive, increasing the cost of using the product.
How Each Abrasive Compares to the Others
Each abrasive has a distinct purpose and, because of that, has specific manufacturing processes that differentiate one from the other. Bonded abrasives can rub off, and coated abrasives are durable, but the cost of longevity is sensitivity. Non-woven abrasives are flexible but work best with finer abrasive jobs.
Each has specific products that work best. That is not to say they will not work on other products, but each has a unique stable of products that matches their strengths.
Wrapping Things Up
In conclusion, choosing the right abrasive for your application is crucial for achieving optimal results. It's important to consider factors such as material type, surface finish requirements, and the tools and equipment being used. By working with our team of abrasives experts, you can ensure that you select the right product for your specific needs.
We encourage you to take advantage of our expert resources by contacting us with any questions you may have. Our team is available to assist you via phone, email, or website chat, and we're always happy to provide guidance and advice on abrasives selection, application, and best practices.