Working with wood almost always requires the use of abrasives, and perhaps the most commonly used abrasive tool is a five inch orbital sander.  These sanders use five inch round abrasive discs and can be used to remove old paint and finish, smooth blemishes, and prepare a surface for finish, just to name a few uses.  Abrasive discs come in many configurations, and it can be confusing when it comes time to make a choice.  Knowing and understanding the different materials and styles of discs will help you choose the best disc for the job, so let’s take a look at the basics.

Backing

The disc’s backing provides the base of the abrasive where the abrasive grains are adhered.  Nearly all abrasive discs fall into one of three backing categories:  film, paper, and cloth.  Film-backed discs are made from a film similar to a flexible plastic, and provide an extremely flat, durable, and consistent abrasive.  Film is great for solid-surface sanding, fine woodworking sanding, or anywhere that abrasive edge tearing is a concern.  Paper-backed discs are made from a special paper for abrasives, featuring a very flat surface, but less durable and consistent than film.  Paper is a great choice for fine woodworking sanding and flat sanding where tearing is not a concern.  Cloth-backed discs are engineered for durability, but are not as flat or consistent than either film or paper.  Cloth is typically used where you need to remove stock or old finish, or sanding steps before final sanding and finishing.

Grains

Abrasive grains put the “sand” in sandpaper, although nowadays that “sand” is typically highly-engineered and specifically-oriented grains.  The grains we’re going to check out are ceramic aluminum oxide, aluminum oxide, and silicon carbide.  Ceramic aluminum oxide grains feature long-lasting, consistent abrasion due to their extreme hardness and orientation on the disc.  Aluminum oxide grains are not quite as hard as their ceramic counterparts, but still long lasting and consistent.  Silicon carbide grains are very sharp and as the disc is used, the grains shear off into a shorter, sharp grain.  This helps keep the abrasive cutting the material, however they won’t last as long nor be as consistent as the other two grains.

Attachment, Dust Collection, and Grit

Now that we know about backing and grains, we need to choose the correct disc for the job.  There are two types of attachment methods:  PSA or sticky back, and hook-and-loop.  Your sander will have a smooth, flat pad for PSA discs or scratchy, hook-covered pad for hook-and-loop.  If your sander is equipped for dust extraction, your sander’s pad will have holes in it.  If it has holes, you’ll want to choose a disc with the same number of holes as your sander’s pad.  Lastly, what grit do you need?  Coarse grits like 80 will aggressively remove material, while finer grits like 150 will refine the material and smooth scratches.

Now that we have the basics covered, get some discs and make some dust!