In order to do good, clean-cut, accurate work it is very necessary that all cutting tools be kept sharp. And it is important that every boy who undertakes toy making have an elementary knowledge of the subject, especially an understanding of how to properly sharpen the knife, the chisel and the plane blade.

If the tool is very dull, with nicks in the cutting edge, it should be ground first on the grindstone. It is quite important that the blade be held at the proper angle, about 25 degrees on the stone. A suitable tool holder, such as is shown in the illustration on Page 26, is a very useful article to have in the tool equipment. The tool is held in place, bevel side down, by thumbscrews, and projects beyond the holder a little over half an inch.

The grindstone should be thoroughly wet to prevent heating the tool and also to insure the washing away of the fine particles of steel from the surface of the stone.

The round shape of the stone causes the bevel of the tool to be concave if held steadily in one position, as shown in Fig. A, Plate 4. Fig. B shows the incorrect result if the blade is not held evenly on the stone. It can be readily seen that the latter result will not make a very sharp cutting edge.

Care should be taken when grinding not to round the corners of the tool.

The theory of the cutting edge of the tool is the same as that of the wedge; the thinner the wedge the easier it is to drive it. However, the wedge, as well as the tool, must be thick enough to stand the strain of being driven into the wood, or the material which is to be split or cut. Too long and thin a bevel, while sharp at first, soon loses its edge through usage, while too blunt an edge makes the tool unsatisfactory to work with.

The grindstone leaves the tool edge rough, or with a wire edge, as it is called. This roughness is removed on the oil stone. One or two drops of thin stone oil should be placed on the stone and the tool placed bevel side flat on the surface of the stone. Work with a circular motion, bearing on the tool with uniform pressure. Turn the blade over, bevel side up, seeing that the blade lies perfectly flat on the stone. Work with a similar motion. Repeat these operations until the blade is as sharp as desired. Wipe the oil from the tool and test by drawing the blade lightly across the thumb. If the blade clings to the skin it will be found sharp enough.

Fig. C, on Plate 4, shows the correct and incorrect methods of oil-stoning the tool blade. Always wipe the stone dry after using, as the oil will dry and gum up the grinding surface if not kept clean.

Tool grinding is an important and rather difficult operation at first and skill comes only with continued practice.

In sharpening a knife-blade on an oilstone care should be taken to keep the blade nearly flat on the stone in order to get a thin, sharp edge. The knife should be sharpened first on one side and then on the other, until the desired edge is obtained.

Fig. D, Plate 4, shows the right and wrong methods of holding the knife blade on the stone. Figures E and F show the results of careless sharpening. Fig. G is sharpened correctly.