Sander Tools
Sander tools use sandpaper to smooth the surface of work pieces. A sander tool is not designed to perform radical shaping of a work piece, like a grinder tool. But sanding tools are essential for making final adjustments to the nearly finished shape of a piece of metal or wood. Sander tools are generally not used on plastic and other materials with low melting points because the heat of friction would melt the material and clog the sandpaper.
Sandpaper is smooth on one side and coated with an abrasive material on the other. The "sand" may be ordinary silica sand, or it may be a more exotic abrasive such as corundum or even diamond dust. The type of abrasive used depends on the nature of the material to be sanded and the finish desired.
Hand-held sander tools can be as simple as a single sheet of sandpaper. But for an even, flat sanding job, a sanding block is the minimum tool required. Other hand-held sanding tools are curved to fit the curves used commonly in furniture. Sandpaper can be wrapped around a rod and used to sand the inside of circular holes.
Power sander tools come in several varieties. A belt sander consists of two electrically-driven pulleys that draw a circular band of sandpaper in one direction, endlessly. A belt sander may be hand-held and moved across the work surface. A vertical belt sander is stationary and the work piece is pressed and moved against the moving belt. Hand-held belt sanders are used to smooth flat surfaces like tables, while vertical belt sanders are used to shape and smooth curved work pieces.
A sheet sander holds a single sheet of sandpaper and moves it back and forth rapidly in short strokes. The vibratory nature of a sheet sander's action makes it easy to move in any direction. Sheet sandpaper is the most inexpensive kind, as well.
A random orbital sander moves sandpaper around in random circular motions. This produces a smoother finish desired on fine furniture and automobiles, but without the grooves worn in by non-random motion. Typically, very fine sandpaper is used with this type of sander. It is possible to get a mirror-like finish with a random orbital sander.
Sander tools are generally used in several stages. Coarse grit sandpaper is used to remove significant amounts of material, leveling the work surface. Progressively finer grits are used to remove less material and polish the finished surface.