Aluminum oxide or silicon carbide? We will help you make the right decision for your next sanding project.

When choosing the right form of sandpaper to use on your next project, your decision will largely come down to which quality of finish you desire, while also taking into consideration the surface material you are working on. Aluminum Oxide and Silicon Carbide are the two most widely used forms of sandpaper across the woodworking and metalworking industries thanks to their versatility, affordability, and consistent performance.

Here are some tips to help you differentiate between the two materials and how you can seamlessly use both aluminum oxide and silicon carbide on your next sanding project.

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Aluminum Oxide

Regardless of if you are sanding wood or metal, aluminum oxide is the most frequently used grain in the industry because it does a pristine job on a number of materials including bare wood, painted surfaces, and metal. Additionally, aluminum oxide is exceedingly durable. The combination of a very good shelf life and lower cost is what makes aluminum oxide stand out over other forms of sandpaper, including silicon carbide

When sanding harder metals such as titanium or stainless steel, aluminum oxide does not have as long of a life as say, Ceramic or Zirconia. These two sanding materials have better durability and run cooler than aluminum oxide when applied to hard metal surfaces. However, ceramic and zirconia are far more expensive than aluminum oxide, and the fact that aluminum oxide is proficient when used to sand many other metals is why it tends to be a more popular choice for professionals across the industry.

The most common form of aluminum oxide is brown aluminum oxide. Other forms of aluminum oxide include pink and white aluminum oxide, which present a stark contrast to brown aluminum oxide. Pink and white aluminum oxide break down much quicker than brown aluminum oxide, but pink and white produce a better finish, meaning pink aluminum oxide and white aluminum oxide are more similar to silicon carbide than to brown aluminum oxide. Brown aluminum oxide provides longer life because the grains crack and break down at a slower rate. This will increases life, but you have to sacrifice some appeal on the finish, which is acceptable in many cases.

When operating cloth-based machinery on a wood surface, Uneeda recommends our RKXO wide belt. For sanding metal surfaces, Uneeda’s most frequently used aluminum oxide products would be PA631 and XA911 for wet operations, which will typically come in a fine grit that provides an excellent finish. Our best seller EKA1000 product boasts antistatic technology, making it an aluminum oxide abrasive that effectively reduces dust and accommodates both narrow belts and wide belts.

Silicon carbide

Silicon carbide is a sharper and harder grain compared to aluminum oxide, but silicon carbide is less durable because it is brittle and has a more narrow shape that wears down at an increased rate. Due to its razor-sharp grains, silicon carbide will have no problem easily cutting glass, plastic, and metal under light pressure. However, hard woods and metals will present more of a challenge. Regardless of sanding wood or metal, silicon carbide and aluminum oxide can be effectively paired together on the same sanding project, especially in woodworking applications.

A customary rule of thumb for sanding is to start out using a lower-number, coarse grit before progressing to higher-numbered grits to add a finer touch. For example, on your average three or four head sanding machine, you may start with an 80-grit wide belt to cut-down and calibrate the item being sanded, focusing on getting the preferred thickness.

In sanding, you never want to skip more than one grit, so the next grit would likely be 120. Both the 80 and 120 grits are likely to be aluminum oxide, but your final 180 grit should be silicon carbide, depending on if your objective is to achieve the best finish without as much concern for belt longevity. This strategy astutely takes advantage of the durability of aluminum oxide, while utilizing the sharpness of silicon carbide to navigate a superior finish. For finishing, nothing is better than silicon carbide because it’s very forgiving. Uneeda’s wide belt ARFSO product is made of silicon carbide and will produce a remarkably consistent finish.