Very often the smooth surface left after a piece of wood has been planed will require only a quick rub over with fine-grade glasspaper before it is ready for varnishing. However, in some cases this is not always adequate.

If the plane iron has small irregularities or is not set up correctly, it can leave slightly raised or indented marks, particularly if a wide board is being smoothed, and if there are irregularities in the surface of the wood, such as knots or twisted grain, areas can be torn out by the plane iron. In these circumstances, a random orbital sander is used for obtaining a fine finish.

The technique is to use progressively finer grades of sanding pad. If there are fairly deep hollows or tear marks, use a very coarse grade to take down the surface until these disappear. Follow this with medium- and then fine-grade abrasive. If there are no deep tear marks, the medium-grade abrasive will be adequate to start with. Change the pads when appropriate, and do not attempt to smooth away large blemishes with a fine grit pad, as it can take hours.

If the surface is finished by hand using a sanding block and glasspaper, the same principles of gradually reducing the abrasive grit size apply. For best results, always move the block in the direction of the grain.

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