There are many kinds of oilstones. Some are pieces cut from natural rock and some are made by pressing a powdered abrasive into a rectangular block. Most stones used for sharpening edge tools are used with oil and are called oilstones.

The oil keeps the particles of metal from adhering to the surface of the stone, or, as we commonly say, keeps the surface from glazing over. Do not use too much oil, only enough to keep the surface well moistened. Oil should not run over the ends or edges. Some oilstones work very much better after being well filled or soaked in oil. It is often better with a new stone not to wipe the oil off after using it. Wipe it only when the surface becomes dirty or filled with metal. Lard oil or other animal oils are better than mineral oils for use on oil stones. Some dealers sell oils especially for use on their oil-stones.

It is a good idea to keep the stone in an iron box as shown in Fig. 144, or in a wooden box. Some prefer to keep the stone in the pasteboard box in which it is purchased, and hold it in the vise while using it, as shown in Fig. 175. The surfaces of oilstones may be made flat by rubbing them on a sheet of sandpaper or emery cloth laid on the bench, or on a smooth flat board as shown in Fig. 164. If you are careful to rub the plane bits and chisels the entire length of the stone, and to sharpen knives and small tools near the ends of the stone, it will keep in good shape for a long time. Most oilstones will break easily and must be handled with care.

Fig. 164. Truing the Surface of an Oilstone.

There are many ways of testing the edges of tools to see if they are sharp. Probably the best method is to use the ball of the thumb as shown in Fig. 165. Another very good test is to try the tool on a scrap of pine. The smoothness and glossiness of the surface of the cut will indicate very well the condition of the cutting edge. You should learn to test the edge with your thumb, because it is quicker and better for most purposes.

Fig. 165. Testing an Edge with the Thumb.