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What Does Open Coat and Closed Coat Mean?

The Difference Between Closed Coat and Open Coat Abrasives

In the world of abrasive sandpaper, you might hear these two terms thrown around. What exactly does open coat and closed coat mean? What are the differences between open and closed coat? And why should I care? This article will break it down into simple terms so you (the buyer) can make an informed decision on which type is best for your operation. The below information applies to both metal and wood working type products. 


What Are Open Coat Abrasives?

Very simply open coat abrasive discs & belts feature more space between the abrasive grains.  The benefit is less loading of swarf on substrates that are soft or sticky.  This prolongs the useful life of the disc or belt.  Some discs and belts also can feature a stearate or anti-static coating used in conjunction to even further prolong the life of the product.  The negatives of an open coat design is that there is physically less abrasive on the product.  This can affect the speed and cut rate of the product, meaning it can take more time for dimensioning or heavy stock removal applications. 

What Are Semi-Closed Coat Abrasives?

Simply put – semi-closed coat abrasives are a middle of the road between open coat and closed coat.  They still feature some space between the abrasive grains to allow swarf to escape, but also benefit from having more physical abrasive on the product.  It is a nice happy medium for good all-around performance on many types of substrates. 

What Are Closed Coat Abrasives? 

As the name implies, closed coat abrasive products have very little space between the abrasive grains.  Close to 95% of the backing material is covered with grains.  The benefit is the product will always have the maximum amount of abrasive in contact with the substrate at all time.  This equates to speed and efficiency.  The down side is close coat products are not well suited to those soft and sticky substrates as the swarf has no-where to escape and thus the belt or disc can clog/load up quickly.  Certain stearate coatings (and grinding aides) can help alleviate some of this. 


Choosing Between Closed Coat & Open Coat Abrasives

Ultimately if you want the most efficient cut rate of the abrasive, closed coat is the way to go, but it has its limitations.  It is best to think about your operation, what the goals are, and the desired outcome.  Answering some of these questions will help in the selection of the right abrasive or sandpaper product for your needs.  There are also more factors to think about, but this is just one that deals with the distribution of the abrasive mineral itself. 

Contact us for recommendations on abrasive belts for your application.

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