As before stated, new planes, chisels, and other edged tools, if of the best quality, are always sold ground and sharpened, ready for use. When used, however, they soon become dulled, and must then be resharpened, and be so kept as to have a smooth, keen cutting edge, in order to do good work and to work rapidly. The method employed for doing this is the same for all edged tools, whether ground and sharpened on one side or on both sides.
Oil stones are used for plane-irons, chisels, and all flat and straight-edged tools; and oil slips, having rounded edges, for gouges, and for all tools having curved edges. They are made of different sizes, and may be found of many and widely different qualities. The best known and most widely used oil stones in this country, and perhaps in the world, are the "Washita," of which the "Lily White Washita" brand, being carefully selected, are the most even in grade and quality, and are the best-adapted natural stone for woodworkers' tools.
The Arkansas oil stones are claimed to be the hardest and finest oil stones in the world. They are composed of nearly pure silica in the form of minute crystals interpenetrating one another, and differ from the Washita only in the minuteness of the crystals and in their more compact arrangement. They are consequently very much harder and cut hardened steel more slowly than coarser grades of stone, but impart a finer and smoother edge to the tool. They are used by wood-carvers, engravers, watchmakers, and others using tools that require a very fine edge or point. They are expensive, and should be used carefully with equal parts of sperm oil and glycerine.
For wood turners' and pattern makers' tools, the- sharpening qualities of the "Washita" are unsurpassed; but the quality differs greatly in stones sold under this name, some being uneven in hardness, and some soft and worthless. No trouble will be found, however, if some good selected brand such as the one mentioned above is chosen. A good size for an oil stone is 6 inches to 8 inches in length, and from 1 5/8 inches to 2 inches in width. The thickness does not matter, but the stones usually vary from ¾ inch to 1¼ inches in thickness.
The oil slip should be about 4½ inches in length, and from 1¾ inches to 2 inches in width, tapering from 6/8 inch on one edge to 3/16 inch on the other, both edges being rounded as shown in Fig. 83.
In using the oil stone, care should be taken to hold the bevel of the tool flat, or nearly flat, on the stone, so that the cutting edge may be kept thin and in easy working condition. The stone is held stationary on the work-bench, and the tool is moved forward and backward over its face. In the use of the oil slip, on the other hand, the tool is held stationary, with the cutting edge or end up, and the slip is rubbed over the beveled surface with a circular motion or stroke, until a keen, sharp edge has again been imparted to it. An abundance of oil should always bo used in order that a finer and smoother edge may be given to the tool, and the pores of the stone be kept clean and fret; from glazing.
In the last few years an entirely new variety of oil stone and oil slip has been placed on the market. It is called the India oil stone, and is made from corundum, the hardest of all mineral substances except the diamond. These stones have wonderful cutting qualities, and differ greatly from other oil stones in that they cut steel much faster, impart better edges, and do not glaze. They are also of uniform texture throughout. India oil stones are furnished in three grades - coarse, medium, and fine - and in all required shapes, a few of which are shown in Fig. 84. Only the "fine" stones are adapted for woodworking tools and for those classes of tools requiring a fine cutting edge.