The Handyman's Book of Tools, Materials, and Processes Employed in Woodworking. Paul N. Hasluck
edge is not sufficiently keen for woodworking, and should be finished on a stone of finer texture. Natural stones are often uneven in grain, but, with care in selection, they can be obtained far better and more lasting than artificial stones. If a natural stone is wetted, the grain will show up clearly, and if it is uneven, or if there are fossils embedded in the stone, unequal wear will be the result, and it will be necessary to rub it down frequently. The colour also forms a guide to a slight extent; if this is variable, the wear will probably be variable. In choosing an oilstone from a number of the same variety, the cutting properties can be judged by rubbing the surface with the thumb nail, but this is only a comparative test, as a rougher surface will always be found on new or freshly rubbed down stone than on one that has been in use for sharpening tools for some time. For this reason, sharpening a tool on a new stone is not a true test of its cutting properties. If a tool-dealer’s catalogue is examined, several varieties of oilstone will be found enumerated in it, the prices of which may be anything from 6d. to 15s. In purchasing an ordinary tool, paying a good price generally procures a good article; but this is not so with oilstones, as bad ones are often to be found among high-priced articles.
Figs. 437 to 440.—Oilstone Slips.
SIZES AND SHAPES OF OILSTONES.
The usual dimensions of an oilstone, excepting the slips (or small stones for sharpening gouges, bead irons, etc.) are: length, about 8 in.; width, 2 in.; and thickness, 1 in. A wide stone should never be selected owing to the difficulty of making it wear evenly, and to the care required to keep the plane irons sharpened on it to the shape necessary to produce the best results. The most convenient width is 1 1/2 in. A stone may be used by making the thickness side the working face; the tool should be moved across the stone from right to left and not always sharpened in the same place. A small oilstone about 4 in. by 1 1/4 in. is useful for sharpening spokeshaves, and pieces of stone or slips of various sizes and shapes are required for gouges, beads, etc. These often have to be rubbed to a particular shape (by one of the methods to be described) to sharpen a tool for some special purpose. A slip as shown by Fig. 437 is used for sharpening router cutters, etc. It will soon wear out of shape, especially the part A, but the shape may be restored by rubbing the stone on a piece of sharp gritstone, using silver sand and water, though a grindstone, if handy, will be preferable. It will be found better for some purposes to use the side of the grindstone, if it be in good condition, rather than the edge. Here also water and a little fine sand will be found an advantage. For sharpening bead irons and gouges this conveniently shaped slip can be purchased at most tool shops; its suitability is apparent. Sections of commonly used oilstone slips are shown by Figs. 438 to 442.
Figs. 441 and 442.—Oilstone Slips.
CASING OR BOXING OILSTONES.
Oilstones may be purchased fitted in a case. To make the case obtain a piece of even-grained timber, fairly hard and tough, free from shakes, about 1 1/2 in. longer, 1 in. wider, than the stone selected, and of about the same thickness. The wood should not absorb oil or break away at the ends. The most uneven side of the stone is placed centrally on the wood that forms the bottom of the case, and is marked round with a scriber. A centre-bit is then used to bore out as much as possible of the wood inside the line, the remainder being cut out with a mortise chisel, and boxed down with a router or old woman’s tooth, finally cleaning out to about three-quarters of the depth of the stone. Another piece of wood slightly thinner is then boxed out in a similar manner to form the lid of the case. The bottom of the case should be eased round the edges with the chisel to enable the stone to drop in without pressure, which will leave sufficient space for the cement used to hold the stone in its place. A mixture of white and red-lead is generally used for this purpose, but should be obtained in a powdered state and mixed with gold-size. If the ordinary tub lead is used, the stone will absorb the linseed oil and will be hardened. Another cement may be made by melting glue and mixing powdered red-lead with it to form a thick paste. This is put into the case whilst hot and the stone pressed into it, the surplus cement being forced up round the edges and cleaned off before setting. After the stone is firmly fixed with the cement, the lid may be fitted on and the case cleaned off true and square, when the plainness may be relieved by chamfering or moulding the top. A bead should be placed round the bottom edge of the lid to break the joint. By placing a block of wood at each end of the stone, a much longer stroke can be taken in sharpening, and the stone tends to wear much more evenly. It also prevents the chipping of the tool should it happen to slip over the ends of the stone while sharpening. It may be better to hinge the cover of the case, and secure it by means of a small brass hook and eye as illustrated in Fig. 443, or the cover may be similarly hinged and secured at the sides. The stone can then be picked up without the cover dropping off. It also prevents injury to the stone by the cover accidentally coming off either on the bench or in the tool basket or box. Figs. 444 and 445 show methods of finishing an oilstone case, and Fig. 446 is a section of a case with a less elaborate moulding. To give the stone a better bearing on the bench when a tool is being sharpened, the bottom of the case between the ends is cut away as shown in Figs. 443 to 445. In addition to this generally a couple of nails or steel points are driven in at one end and filed off to a point, leaving about 1/8 in. below the bottom of the case (see A, Fig. 447). This gives the case a firm grip on the bench, but scratches it. A better plan is shown in section by Fig. 448. In this two small cylinders of india-rubber are glued into two centre-bit holes of about 1/4 in. or 3/8 in. diameter bored at one end of the case, one on each side. The pieces of rubber are cut to size with a knife previously dipped in water, but are made about 1/32 in. longer than the hole is deep, so as to project below the surface. They may be cemented in with thick knotting or shellac varnish. The friction of the rubber will effectually prevent the stone from slipping about when a tool is being sharpened, and the rubbers do not injure any surface upon which the case may be placed. An oilstone case should be well French polished, the polish being tinted with a little dragon’s blood or other stain if preferred. It is much easier to keep the case clean if polished than when oiled.
Fig. 443.—Oilstone in Plain Case.
OIL FOR USE WITH OILSTONES.
Oil is used not only for assisting the stone to produce a keen cutting edge, but as a lubricator to prevent the stone heating the tool, and to prevent the entrance into the stone of the metal particles rubbed off the edge of the tool whilst sharpening. The oil should not gum up or harden if left, or it will cause the stone to glaze. Either neat’s-foot oil or sperm commonly is considered best for oilstone use, all others hardening the surface much more quickly. Good for the purpose is lard oil to which sufficient petroleum has been added to prevent it becoming thick in the can in cold weather. Sweet oil or vaseline thinned with petroleum makes a good sharpening oil, in fact, any oil of animal extraction mixed with mineral oil may be used, but vegetable oils that are obtained from seeds and nuts and are used for making paint should be avoided. Sweet oil with the addition of about one-eighth of paraffin