Wood chisel or plane iron, both have a bevel that forms the cutting edge. This is the only part that can be sharpened. The actual sharpening is done on an oil stone which generally has two sides with different grains. The grinding stone is not used to sharpen but to rectify a blunt tool.

Place the stone on a rag or a piece of wood. This will prevent you from staining your workbench with oil. Start on the side of the stone with the largest grain and wet it with oil.

Place the bevel of the blade on the oil and find the right angle by tilting it slightly back and forth. The backflow of the oil indicates that the bevel is flat.

Striving to maintain this angle, make figure-eights by pressing the bevel onto the stone. It takes some practice to hold the iron without wobbling and to move it without the angle changing.

When the metal of the bevel has taken on a uniform color that indicates that it has been well ground, briefly pass the reverse side flat on the stone to remove the morfil. This is the small metal filament that will have formed at the tip of the blade.

Turn the stone over on its thin side and repeat the operation. This time it is only to refine it. The edge will also be finer. As soon as it comes off, don't insist, the edge is ready, which you can check on wood or on a corner of your cloth.

To preserve your tools, make it a habit to never put them on the cutting edge. Don't leave them unprotected in a box with other tools. Of course, as with all sharp tools, you don't use a chisel by forcing it towards you.