Floor sanding can be done by hand, but electrically driven sanding machines are used almost exclusively today. These machines are usually available from rental agencies and some paint stores/home centers which also supply the sandpaper. Some handwork is ususlly necessary in less accessible places.
Sanding machines may be either the drum type or disk type (floor polisher). In drum sanders the sandpaper is mounted on a cylindrical drum that rotates on an axis parallel to the plane of the floor. Thus the sandpaper makes its scratches in straight lines in the direction of movement of the machine. In disk sanders the sandpaper is mounted on a disk that rotates in a circle in the plane of the floor. As a disk sander is moved over the floor, the grits make spiral scratches that necessarily cross the grain of the wood. A drum sander, however, cannot reach the last few inches of floor nearest the baseboard. Electric edgers, which are small disk sanders, are available for sanding these edges of the floor, or they may be done by hand.
Sandpaper acts by gouging fine slivers from the wood surface, leaving scratches, the size of which is governed by the size of the grits on the paper. Coarse grits act rapidly, but the scratches they leave are conspicuous, especially if they cross the grain of the wood. Fine grits act slowly, but the scratches left are too small to see. Scratches are least noticeable when they run with the grain of a wood. Scratches must be especially fine to escape detection on a wood with close texture, such as maple, and must be still finer to remain unnoticed if they cross the grain of the wood.
In sanding a floor, time is saved by starting with coarse sandpaper to remove the grosser roughness and imperfections and to make the floor level as quickly as possible. The scratches left by the coarse grits are then removed by successive sanding with a finer sandpaper. The scratches left by the last paper should be too small to be observed even after the finish has been applied.
Before beginning the sanding procedure, carefully sweep all dirt, dust and other debris from the floor. "Set" all nails that may be protruding either in the floor or baseboard so that the sanding machine will not be damaged. Sometimes, only two sanding cuts are needed on a new hardwood floor, but if the floor is at all uneven or if a particularly smooth finish is desired, three cuts will be necessary. The first cuts should be done with a coarse or medium abrasive, always ending with a fine abrasive. A smoother finish will result if the final sanding is done with the floor polisher or disk sander. Of course, more passes with finer paper will result in a smoother finish.