Here's What's Wrong With Your Sanding Technique (And How To Sand Wood Like A Pro)

Today, I have 40 years of experience as an expert woodworker and furniture maker ... but in the beginning, my first job in my dad's cabinet shop was being the "sanding boy." 

"Yay, it's sanding day!" said no woodworker, ever. It took me years to learn how to sand wooden surfaces effectively. Sanding isn't fun, so doing it efficiently is a real benefit. The goal of sanding wood is to smooth the surface until it is ready to accept a finish, and most folks work too hard at the task, spending too much time, because they have learned improper techniques like skipping grits or sanding in the wrong direction. Well, here are some suggestions to get the job done quickly and well. 

My first sanding tip: Start with a suitably coarse grit of sandpaper. Most wood purchased at a lumber yard or big box store is surfaced lumber (as opposed to rough cut lumber, right off the sawmill), which calls for 60-grit paper. Whether by hand or with a rotary orbital (RO) sander, methodically sand the wood to a uniform surface. The fibers of the wood will look and feel rough, as there are marks or "scratches" caused by the 60-grit paper. Pay attention to them: They are the key to your next steps. Change your sandpaper to 80-grit and repeat the process. Your goal is to completely remove the 60-grit sanding marks with those made by the 80-grit paper — and when you've achieved that goal, move on to 100-grit paper to remove the 80-grit marks. Next up, 120-grit, 150-grit... you get it. Here's the most important thing: don't skip a grit. If you intend to paint the wood, sand up to 150-grit. If you plan on applying a clear finish like polyurethane, go to 220-grit or preferably, 320-grit. 

The above process will work well regardless of whether you are sanding by hand or using an RO power sander, but the methods are completely different. When sanding by hand, start sanding by moving the 60-grit sandpaper, wrapped around a sanding block, diagonally to the grain of the wood. This will ensure that you are removing the wood fibers evenly and that you can see the sanding marks very clearly. When the entire surface looks the same, grab your 80-grit sandpaper and sand diagonally across the grain, but in the opposite direction. Next, switch to 100-grit and change directions again. Continue in this manner until you are two grits away from your final finish (100-grit for painted surfaces and 150 for clear finishes). For the last two sandpaper grits, sand with the grain of the wood, removing the previous sanding marks. You've now prepared a perfect surface for finishing.

If you're using a handheld power sander, the process is similar but not identical. First, move the sander slowly across the wood's surface. How fast? Here's a good way to find the proper speed: Grab a twelve-inch ruler, put a finger on one end and slowly count to twelve while moving your finger along the length of the ruler. It should take about 12 seconds to get to the other end of the ruler. 

When using a RO sander, move it about one second per inch. Most folks move the sander far too fast. Move the machine with the grain and overlap your passes by about 1/3 of the sanding disc. Don't skip a grit: You'll have great results. Also, don't push down on the sander, let its weight do the work, and remember to brush (or vacuum) the sawdust away after each grit.