Today's woodworkers finish and shape wood products with sanders more often than with the more traditional wood planes and scrapers. Sanders use different shapes and different drive systems to accomplish different stages of work. The sander used to shape the edge of a board or smooth a rough surface is not the same machine used for delicate finishing work.
Oscillating or random orbit palm sanders vibrate in a slightly eccentric horizontal pattern which leaves no regular patterns behind. While belt and disc sanders will cut arcs and lines into a wooden surface, palm sanders nearly erase their own tracks. Palm sanders won't remove much wood and are not efficient for shaping. These small machines can polish small corners as well as large surfaces. Palm sanders use ordinary sandpaper--to prevent tearing the abrasive sheet be careful to fit the paper tightly to the base. Some palm sanders have two settings--one eccentric and one back-and-forth. Both are used in finishing applications.
The drive drums of belt sanders spin a continuous belt over a supporting metal backing plate. The belt sander design exposes a lot of abrasive surface to the work and removes stock quickly. If the machine is kept flat on the surface of the wood, stock removal is even. Tipping the machine or applying uneven pressure can grind grooves into the work and quickly ruin belts. When a belt's grit becomes clogged with dust the belt sander may even scorch the workpiece. Portable belt sanders do much of the work that was once the role of the wood plane.
Disc sanders--a very old abrasive design--use the large face of a rotating wheel as the sander's backing plate. A center arbor locks the sanding disc in place--temporary adhesive or simply a high-friction surface keeps the abrasive from shifting. This design wears more quickly in the outer section of the wheel than toward the center, because speed of revolution increases toward the rim. While disc sanders work well when abrasive discs are new, results quickly become uneven.
Larger stationary machines in either belt or disc designs require operators to pass the lumber being worked over the top of either a belt or table. Industrial quality belt sanders can quickly bring even laminated end grain butcher blocks to an evenly polished finished surface. Higher speeds and more power create more safety hazards as well.
Drum and disc sander attachments fit most power drills and drill presses but won't substitute for well designed electric sanders. Small drum sanders and discs lack enough surface area to do much work before wearing out. Flap sanders and other patented gimmicks yield similar results and over the long term are very expensive. Electric sanders usually include dust collection systems to reduce the health risks of breathing clouds of wood powder. That safety feature is not part of sanding accessory systems.