How To Choose the Right Sandpaper for Wood Projects
A pro woodworker explains what you need to know about sandpaper for wood, so your next project turns out perfectly.
Sandpaper is ubiquitous in the wood shop, and there are so many variations it can be overwhelming to a beginner. Is it best to sand to 180 or 220? What are those spongy sanding blocks for? Why are some sandpapers different colors?
The world of abrasives can be vast and tricky to grasp, but let’s stick to what’s generally useful in the wood shop. I’ll give you all the information you need to be successful in your sanding endeavors on your next project.
Understanding Sandpaper for Wood: Grit Size
The first thing you need to understand is grit size. Sandpaper is nothing more than tiny particles, most often made of metal compounds, that adhered to a backing — often, paper. The size of those particles determines the grit size.
The lower the number, the larger the particle size and the coarser the sandpaper will be. That removes material faster while leaving a rougher surface. The higher the number, the smaller the particles, which leave a smoother surface. There’s no end to how long and how fine you can sand, but for our purposes we’ll focus on four main grit ranges.
Coarse grit = 36 to 80: This is best for fast stock removal, such as smoothing the live edge of a slab or sanding down rough-sawn surfaces.
Medium grit = 100 to 180: This will remove any mill marks from your machines and give you a generally clean and clear surface. Some finishes will recommend only sanding up to 180 to allow the finish to “bite” onto the surface of the wood, so be sure to read the instructions before applying your finish.
Fine grit = 220 to 400: I generally sand up to 220. This gives me the best clarity of grain on the surface of the wood. I may sand with 400 grit sandpaper or an equivalent abrasive cloth after the final coat of finish to give a nice, smooth surface to the piece.
Polishing grit = 600 and up: These grits, for polishing finished surfaces, are only occasionally employed in the wood shop.
Bonus fact: Europe has a different grit scale than the U.S. If ever you see the grit size labeled P-180 or P-220, that’s the European scale. And while it’s not an exact equivalent, it’s close enough. I consider it basically the same.
Hand Sanding vs. Machine Sanding
Depending on your sanding setup, you may need different styles of sandpaper. The most common are as follows:
Sheet sandpaper: You can find sanding sheets in various sizes, but the most common are 9-in. x 11-in. and 9-in. x 3-in. These sheets generally have a smooth paper back and are fairly rigid when folded. They can get into crevices and corners that machines can’t, letting you sand every square inch of your project.
Sanding blocks: These semi-rigid, spongy blocks are often sold at hardware stores for a significant markup over sanding sheets. While they have their useful applications (drywall sanding comes to mind), they are not all that useful in the wood shop. Don’t waste your money. Buy sandpaper sheets and make your own sanding blocks!
Sanding discs: These discs are generally five or six inches in diameter, so make sure you know the size of your sander. There are also two styles of backing: hook-and-loop (AKA H&L or Velcro) and pressure sensitive adhesive (PSA). While H&L discs are far and away the most common, don’t assume every package is H&L. Make sure you get the right disc for your machine.
Note: Here are Family Handyman’s picks for the best sanders for wood projects.
Types of Sandpaper
Here are the basic industry terms:
Aluminum oxide: Sometimes abbreviated AO, it’s the most common type of abrasive. Nearly all the sandpaper you buy for wood, whether as sheets or discs, will be aluminum oxide. These sheets are typically brown or maroon in color.
Zirconia alumina: Abbreviated Zirc, it’s a long-lasting abrasive often employed in aggressive stock removal, such as the flap discs you might purchase for an angle grinder or a belt sander for shaping wood. They’re most often blue or green.
Silicone carbide: These abrasives are versatile, durable and generally more expensive than AO or Zirc abrasives. You will often find this abrasive if you purchase high grits (roughly 400 grit or up) or sandpaper at a metal working or auto body shop. These are generally black and the backing often water-resistant, making it the best choice for wet sanding applications such as polishing a finished tabletop.
Choosing the Right Sandpaper for Your Woodworking Project
Despite all these grit ranges and abrasives types, choosing the right sandpaper for your woodworking project is simple if you follow these general guidelines.
Shaping and stock removal: Stay in the coarse range, between 36 and 100 grit.
- Paint and finish removal: Refurbishing an old table? That starts with removing old paint or finish. For this, I would start with 80 grit and work my way up to 150 grit.
Prepping a surface for finishing: Anywhere between 120 and 220 grit is fine, whether you sand by hand or with a power sander.
Polishing a wood surface after applying finish: If you want to polish up a wood surface to really make the finish shine, between 400 and 800 grit sandpaper works best.