Before attempting to sharpen your tools yourself it would be well to read the advice given on page 22 under Care of Tools.

The general process of sharpening edged tools is first to grind them to as keen an edge as possible on the grindstone, or the emery-wheel, then to smooth down the coarse edge left by the grindstone by rubbing on a fine stone with oil or water, and finally stropping on leather. The grindstone must be kept wet while grinding or the heat caused by the friction of the tool on the dry stone will ruin the temper of the steel. Besides, the water carries off the waste particles of stone and steel. Stand on the side towards which the top of the stone turns. The tool can be ground with the stone turning from you, and, in fact, this usually seems the natural way to a novice, but it is usually more difficult to grind uniformly in that way and too thin an edge (a " wire-edge," ragged but not sharp) is apt to be produced, the removal of which is difficult without further damaging the edge and delaying the final sharpening.

Fig. 669.

To grind the point of a knife, it can be moved back and forth lengthways with a curving motion, while resting flat on the grindstone, and to grind the straight part of the blade, it can be allowed to bear very slightly harder near the edge of the stone than elsewhere, as it is passed back and forth.

1 Another method of doing this is to find a true surface to stand the legs on and measure the distance the free leg rises from the surface - 1" for example. Do nothing to that leg, of course, or to the one diagonally opposite, but saw 1/2" from each of the two other legs. Suppose, for example, the legs a, b, and c touch (Fig. 669), and d rises \" from the floor. Make a and c each 3/8' shorter. Of course you cannot hit it exactly by this method, but a few strokes of a tool will finish the work.

To grind a chisel, grasp the handle with the right hand, hold the blade in the left hand with the fingers uppermost and near the cutting-edge. The arms and wrists should be kept as rigid as possible, the former at the sides of the body, so that the tool may be held firmly against the motion of the stone. Lay the chisel with slight pressure quite flatly on the stone and then raise the handle until the bevel touches the stone. As you grind keep moving the tool slowly back and forth across the stone, which helps keep the edge of the tool straight and prevents the stone being worn away too much in one place. Use plenty of water.

The common way of holding the tool on the stone is the one just described, but it can also be held at right angles to this position, so that, in the case of a chisel, for instance, the grinding action of the stone instead of being from the edge toward the handle is from side to side of the blade. The tool is ground quicker and easier by this means, and it is a good way to reduce the edge to shape, finishing the grinding by the regular method.

You will see that the curvature of the stone will tend to give the bevel a slight curve, in whatever position the tool is held, which is advantageous in the common way of grinding. When held so that the stone grinds from side to side of the blade the tool must be continually turned a little in the hand so that each part of the edge will bear in turn on the stone, as, the tool edge being flat, and the surface of the stone rounding, the tool would otherwise be ground hollowing. It is harder to hold the tool in this way, however, without its slipping or making nicks or grooves in the stone, and you had best learn to grind in the ordinary manner.

Try to grind squarely across the chisel - that is, to have the cutting-edge at right angles to the lengthways edge of the tool. Apply the square at intervals to test the accuracy of the grinding.

The angle for grinding the bevel of such tools as the chisel is about twenty-five degrees, but when used for very hard wood the angle should be slightly greater, or the edge may be broken.

Do all the grinding on the bevel. Do not apply the flat side 37 of the tool to the grindstone. Any slight burr or turning over of the edge on the flat side should be taken off by the oilstone.

If the edge is badly nicked or broken, you can first straighten or grind it down roughly on the side of the stone or by holding it nearly at right angles to the stone - but with the latter turning the other way - before grinding in the regular way.

To tell when the tool is ground sufficiently, hold the edge in front of you toward the light. If the edge can be seen as a bright shining line it is a sign that the tool is dull. It will not be sharp until this bright line has been removed, and the edge has become invisible, for a really keen edge cannot be seen by the naked eye. Bear this in mind, as it is the final test and the simplest way to tell when to stop grinding.

In grinding on a grindstone and in rubbing on an oilstone, the great difficulty is to keep the same angle between the tool and the stone, as the natural tendency in moving the tool is to rock it back and forth and thus alter the angle between the blade and the stone. An arrangement can be bought which preserves the desired angle without effort on the part of the grinder. A little ingenuity will enable you to rig up a guide or gauge with a piece of board which will enable you to replace the tool on the grindstone at the same angle.

The plane-iron is sharpened in the same way as the chisel, only, being wider than most of the chisels you are likely to use, it requires more care to sharpen. The plane-irons can be ground to a somewhat more acute angle than the chisels, although the jack-plane, which is used for rough work, may require more strength at the edge.

In rubbing the edge upon the oilstone, do not attempt to smooth down the whole bevel made by the grindstone, but first lay the tool lightly on the stone as shown in Fig. 670a, then raise the handle until the upper part of the bevel is very slightly raised, - barely enough to clear the stone (Fig. 67 od), - and then proceed with the whetting, thus making a second or little bevel at the edge (Fig. 671).

Fig. 670.

Fig. 671.