It’s hard to tell if you've sanded a board smooth when you can't feel your fingers. That’s the dilemma with random-orbit sanders, which work the wood's surface using a round pad that not only spins but also slides from side to side randomly in all directions—in effect orbiting the center of the device. That shaking motion is great for removing material without gouging the wood. Unfortunately, it also rattles your hands, causing numbness and even lasting nerve and circulatory damage.