What’s new with abrasives

While sandpaper comes as discs, belts, sheets and rolls in a huge variety of shapes, widths, grits and backings, its most important element is still the abrasive – the material that actually does the work. Woodshops have traditionally used open coat aluminum oxide for softwoods, and a closed coat for hardwoods. Silicon carbide has some serious fans, too, especially in shops that process harder and more dense hardwoods. Stearate coatings on these grains helps avert clogging, and aluminum oxide is more popular because it fragments easily when sanding wood. That process, called friability, constantly reveals new, sharp edges.

There are new, sharp solutions in this arena all the time, but most of them have nothing to do with the actual abrasive. Robotics continue to make significant inroads in sanding, and woodworking is following the lead here of auto manufacturers. That sector is experiencing one of the worst droughts in qualified labor and has replaced the majority of its production lines with robots. It makes sense: robotic arms can move quickly and precisely, and they can apply exactly the right amount of pressure and speed during a sanding operation. Plus, sanding has always been regarded as a health issue, so removing humans from the line is a logical cost-saving step. Even for small woodshops, the future of abrasion lies at the end of a cobot arm.

Beyond that, the most dramatic progress of late in actual abrasives has been in backers, where meshes and new hole patterns have dramatically improved dust collection by allowing more waste to enter the vacuum stream.

One of the manufacturers leading the way in backers is Mirka (mirka.com), a company that was founded in Helsinki, Finland in the 1940s. In 2001, Mirka pioneered mesh backing with the introduction of Abranet, and that has changed the way that many shops approach sanding of both raw wood and cured coatings.

Mesh is exactly what it sounds like, a flat net that is coated with abrasive minerals. It’s more holes than whole. The Abranet line uses ceramic abrasives bonded with resin on a polyamide net mesh. Polyamides are natural or synthetic polymers, which in lay terms are essentially just substances made up of large molecules. Familiar natural examples of polyamides would be silk and wool.

This porous backing improves the longevity of the abrasive, and also speeds up the sanding process. The flexible mesh resists edge wear better than paper backers and doesn’t inherit the problems of uneven thickness that can be part of a woven cloth backer. But the real advantage is the porosity, where fines can be sucked right through the disc and deposited into the collector’s airstream. The design creates an environment where the entire surface acts as a recovery agent, rather than relying on strategically located hole patterns. Mirka says that its “net abrasive solution is 99.97 percent effective at removing dust particles that are smaller than 0.3 cm in size.”

Klingspor (klingspor.com) also offers a mesh backer. Called Klingnet, it comes in 5” and 6” discs in grits from 120 to 800. Speaking of discs, Klingspor offers woodshops a way to convert old PSA disc sanders to hook & loop by using its Black Hook material. A woodworker decides what size disc and which hole configuration is needed, and then affixes a pre-cut disc to the old pad. That can be found in Klingspor’s 2024 catalog, which is available online as a PDF file. The company offers a broad range of products using both aluminum oxide and alumina zirconia abrasives.

Klingspor says that “it’s always best to use a closed coat if loading isn’t an issue”, and that brings up a significant area of concern for woodworkers. Some species such as oily teaks and sap-heavy softwoods will do better with an open coat. In that case, the grains cover about half of the backer (or a little more), so there are gaps where larger particles can go. That helps reduce glazing and makes it easier for a resin-based cleaning block or even a compressed air jet to dislodge them and renew the abrasive. Open coats can run a bit cooler too, so the saps and resins in wood aren’t quite as susceptible to melting. Open coats work well with SPF and even cedar, but they’re aggressive and are generally used in coarser (smaller number) grits, so the shop may need to move to a semi-open or closed grit for fine sanding.

3M (3m.com) is also pioneering new abrasives. The company’s Cubitron II product has a ceramic coating with a friability that reveals new cutting edges in a manner that delivers very consistent performance. On the company’s Stickit line of J-weight cloth-backed discs, this ceramic is arranged in an open coat that’s designed to prevent clogging. 3M says that “the Stickit backing allows for easy application and removal, and a liner prevents dust and debris from contaminating the adhesive.” The pressure sensitive discs are stuck to a flat pad and come in a variety of hole configurations. The Cubitron abrasive itself is a precision-shaped, triangular, ceramic grain that is “designed to slice through the substrate, rather than gouging or plowing like conventional abrasives, resulting in a disc that cuts up to two times faster than conventional abrasives.” There is a static resistant coating over the particles that provides additional dust control in some woods, and the resin bond resists heat build-up.

Uneeda (sandpaper.com) has developed the Filmtek line that uses a waterproof, highly flexible and very durable film (it’s actually a plastic) backer that outlasts paper backers by a factor of two or three, depending on the application. What’s most significant about the Filmtek product is that the company has been able to bring the price down to the same neighborhood as paper discs. The abrasive on the blue Filmtek discs and sheets is aluminum oxide, and the film backer is a solution that offers the durability of cloth plus the smoothness of paper. Filmtek products are also stearated, and that coating adds a soapy lubricant quality to the abrasive. While stearation is usually applied as a topcoat, in this case it’s incorporated in the resin. It both cools the process and allows fine particles to escape, so that they don’t clog the spaces between the abrasive grains. Filmtek is available in a variety of shapes, with PSA or hook-and-loop fixing, and in a wide selection of hole patterns.

The Gator family of products from Ali Industries (gatorfinishing.com) offers random orbit sanding discs in both traditional aluminum oxide and also zirconium oxide (ZrO2) options. This latter may sound familiar because zirconium is widely used to make things such as dental implants and manmade engagement rings. Zirconium oxide has excessive hardness and chemical neutrality, and forms an advanced ceramic product that is significantly tougher than aluminum oxide. It has impressive heat resistance too because of its very low thermal conductivity properties, plus high strength and friability (self-sharpening).

Global Abrasive Products (GAP, online at globalabrasiveproducts.com) also makes an aluminum oxide product but it’s on a film backing rather than paper. Branded as FilmBac, it is produced as PSA discs with a stearated coating that comes in grits from 80 to 2000.

The newest addition to the Rhyno line from INDASA (indasa-abrasives.com) is called Rhynogrip HT and it has been on the market for a couple of years now. Available in strips and discs on a grip (hook and loop) fastening system, it offers a very uniform scratch system along with good flexibility and high initial cutting action. The aluminum oxide abrasive has a high strength resin bond that minimalizes grit shedding, and an advanced clog resistant coating. Offered on both D and B weight latex papers, it comes in grits ranging from 40 to 2000.

Norton Abrasives (nortonabrasives.com) introduced its new RazorStar line of highly aggressive discs and belts in January. The collection was designed for metalworking, but that won’t stop renovators, refinishers, wood carvers and other woodshop pros from using them when they need to shape or remove a lot of wood quickly. The discs and belts have an engineered, shaped, ceramic grain that cuts quickly but doesn’t generate too much heat.

DeWalt (dewalt.com) introduced the new Elite Series of abrasive grinding wheels last May. While their primary purpose is not abrading wood, they can be quite useful on the jobsite when dealing with demolition issues, or in the shop when working with mixed media materials. The new wheels have a Pressure Pact design that boasts high grain density with increased grain availability, for higher performance and longer life. They also have self-sharpening crystalline grains that enable fast grinding.

The new G0967 from Grizzly Industrial (grizzly.com) is a 20” variable speed disc sander. The 2-hp, single-phase machine has both X and Y miter slots, a tilting table, and a built-in motor brake.

And for shops with unusual abrasive challenges, Laguna Tools (lagunatools.com) makes hundreds of sanding accessories plus machines, including single and double brush sanders. These can often handle shapes and challenges that standard abrasive machines just can’t tackle.  

This article was originally published in the March 2024 issue.