Excerpt from The Canadian Builder
The Sharpening of Woodworking Tools A Valuable Artitle for the Practical Workman from The National Builder The tools used toi woodworking are ground aud sliarponed to more acute angles than those used for cutting harder substances, such as metal. The most suitable angle for any given tool is decided by the character of the material it has to cut. As there is a ciinsiderable ilitference in the hardness of different kinds of wood, the tools used for cutting it vary also in their cutting angles, tools used for soft wood being more acute than those for hard. This does not mean that tools must be kept specially for eacli kind of wood, or must be reground to suit eacli. A patternmaker working with soft pine or a joiner working chiefly with whitewood or cypress would sharpen their tools suitably for these woods ami use them on hard woods occasionally, but if their work was chiefly with hard wood they would find the tool edge too acute. They would become dull very quickly, and if lieavy cuts were taken would get broken and notched. A more obtuse angle would give a mort durable cutting edge. necessary. The sharpening angle on a newly ground tool can be almost the same as the grinding angle; but as the edge wears back, as in Pig.2, the chisel has to be tilted more and more on tlie oilstone to avoid a wide sliarpening facet. Grinding is a simple matter, requiring chi(;fly a knowledge of the most suitable angle to gi-ind it. It is done either on a grindstone or emery wheel. In the latter case great care must be taken not to heat the tool. The pressure must be very light and the tool should be frequently removed and examined. An emery wheel on whicli water can be used is preferable to a dry one. A grindstone cuts slowly and the pressure on the tool must be comparatively heavy. Water is always used on it to prevent the stone from glazing. A person accustomed to the work will grind a tool more neatly than a beginner. The facet should be straight and uniform, not broken up into a number of Hats with an edge perhaps not keen or not straight. FijiUfti 1 Fifui-f i Figure 4 Figui-c 5 Fig. 1 shows two chisel edges, one ground for hard wood and the other for soft. Another reason for the difference is that the firmer chisel is intended for rougher work than the paring chisel, and is often driven with a mallet. It is the chisel used for ordinary work, and is shorter and thicker than the one intended for paring. Tlie difference in their angles is often greater than illustrated. Tlie angles are not measured in any way, but the workman judges by his eye when they are about right as he grinds them. In all cases the angle of sharpening on the oilstone has to be more obtuse than the grinding angle. This is necessary in order to save labor and time in sharpening. The ground facet of a chisel extends perhaps half an inch from the edge, and if this facet was laid flat on the oilstone and rubbed till the edge was keen, it woiald be a very slow process, for the oilstone cuts very slowly indeed, compared with the grindstone. By tilting the chisel slightly a very narrow facet is rubbed, just sufficient to make the edge keen and leave most of the ground facet untouched. This narrow facet made by rubbing on the oilstone is shown by the double lines close together at the edges of the chisels in Fig.1. After repeated sharpenings without grinding the chisel In the latter res)ect a plane-iron is much more difficult to deal with than a chisel because of the greater width and the necessity of a correct edge, slightly curved, or bellied, more or le.ss according to the kind of plane. A chisel can simply be ground straight at its edge, and it does not matter if it is not quite at right angles with Kit;ii l-iuiiedge becomes thick, as in Fig. regrinding is tlie sides of tlie chisel. Figs.3, 4 and oshow tools being ground a cliisel, plane-iron and hatchet respectively. They are generally moved to and fro sideways on the stone to lessen. Это и многое другое вы найдете в книге The Canadian Builder (Classic Reprint)