Oilstone

From OED

Large quarries of excellent oilstone have been Washita River opened oilstone, of fine quality, is abundant in the 1. A flat, smooth, fine-grained stone whose surface is moistened with oil for sharpening tools; stone suitable for use in this way.

1585 J. HIGINS tr. Junius Nomenclator 412/1 Cos cretica,..an oylestone, or a Barbars whetstone smeared with oyle, or spitle.

1675 R. HOOKE Diary 28 June (1968), Lamb bought oyle stone, 18d.

1710 Philos. Trans. 1708-09 (Royal Soc.) 26 493, I set it sometimes upon an Oyl-stone or Hone.

c1790 J. IMISON School of Arts II. 44 The tools necessary for engraving are, the oil-rubber, burnisher, scraper, oil-stone, needles, and ruler.

1815 J. SMITH Panorama Sci. & Art I. 24 They will leave the surface of metal..almost as smooth as an oil-stone.

1885 Spon's Mechanic's Own Bk. 242 Oilstones.{em}These are of several kinds, the best known being the Charnley Forest, Turkey, Arkansas, and Washita brands.

1947 J. C. RICH Materials & Methods of Sculpture x. 300 Fine oilstones are generally used for sharpening flat chisels.

1992 C. MCCARTHY All Pretty Horses (1993) II. 112 The man..came back with a wooden rack of butcher and boning knives together with an oilstone and set them out on the paper.

2001 Model Engineer 186 136/3 To give the form tools a really keen edge, the top..should be rubbed on a flat oil stone.

Oilstones are made of both natural stones and artificial materials. The natural stones include hard Arkansas, soft Arkansas, and Washita stones. They are fairly uniform in hardness and are used for producing fine to very fine cutting edges.

Artificial stones are made from aluiminum-oxide and silicon-carbide abrasive grains formed into the de­sired shape. Since abrasive grains are made in different sizes, it is possible to make oilstones with various sizes of grains of uniform hardness that produce coarse to fine cutting surfaces. Except for the diamond, natu­ral stones are much softer than artificial stones.

The hard Arkansas stone, in shades of white to gray, is very hard, with extremely fine cutting surfaces. It is so dense that the oil does not penetrate deeply and only a few drops are required to carry away the waste particles of steel (Fig. 1-17). For put­ting a keen edge on the finest tool, there is no substitute for this stone. It is used principally for stoning woodworking tools when finer cutting edges are desired. The comparatively high cost of the stone is offset some-what by its extreme hardness, result­ing in long life.

The soft Arkansas stone is softer than the hard Arkansas stone and is more porous and faster cutting. It is used for stoning woodworking tools and gives an adequate cutting edge (Fig. 1-18) .

The Washita, it natural stone, is softer and faster cutting than the soft Arkansas stone. It produces a moder­ately smooth, long-lasting edge on woodworking tools. The aluminum-oxide stone is made of the same abrasive as is used for making grinding wheels. It is brown­ish and the structure is so porous that the oil penetrates deeply. Because of its cutting ability and its hardness, this stone is highly recommended for stoning a keen, fine cutting edge on woodworking tools (3, 10) . It is made in coarse, medium, and fine grades. In some cases, aluminum-oxide stones are saturated with oil during the man­ufacturing process.

The silicon-carbide stone is gray and the abrasive grains are very hard and brittle. Because they fracture easily, the grains stay sharp and are fast cutting. The stone cuts freely by applying only light pressure. The manufacturer, to make it cut more easily and smoothly, usually impreg­nates the stone with oil. This stone is made in coarse, medium, and fine grades. See Figs. 1-19, and 20.

Selection of oilstones

Before selecting an oilstone, one should understand the sharpening process. Sharpening means that steel is actually cut and removed from the tool to bring it to the appropriate cutting edge.

In order to serve satisfactorily for all stoning jobs, oilstones must be selected on the basis of grain size, hardness, brittleness, and toughness. With these characteristics in correct proportion it will produce a suitable cutting edge on a particular type of tool.

If the tool requires a coarse edge, then a coarse, fast cutting stone is needed. For a finer cutting edge, a fine, slower cutting stone is required. As an extreme example, a stone used for sharpening a shovel would not he suitable for producing the fine cutting edge required for razors, engineering tools, and surgical instruments.

Since general woodworking t( quire a medium cutting edge, it may appear that a medium-grain oilstone would be most suitable for sharpening them. But this is not altogether true. A keen edge can be more quickly obtained by first stoning the tool on a coarse surface and then finishing the edge to the desired fineness on a stone which has a fine surface (3, 7) . Oilstones are made in a large variety of shapes, sizes, and types to meet the requirements for all stoning jobs. The bench stone in sizes 6" x 2" x 1_" or 8" x 2" x 1" is commonly used for general purpose sharpening. If artificial stones are used, the combination stone, coarse on one side and fine on the other, will prove to be very convenient. The coarse side can do the preliminary stoning, the fine surface the finishing (Fig. 1-21) . Other stones that are needed for special stoning jobs are the round edge slip, the special gouge slip, the carving tool slips, the auger bit stone, and the round and triangular shapes.

See Fig. 1-22, 23, 24, 25, 26, 27 and 28. Oilstones used for stoning carbon and high-speed steel must be made soft enough to cut freely and yet sufficiently hard and tough to hold their shape. The aluminum-oxide stone meets these requirements as well.

Silicon-carbide stones are especial­ly recommended for sharpening car­bide-tipped tools, and are quite satisfactory for carbon and high-speed steel if not too much pressure is ap­plied during the stoning process.

Care of oilstones

Plenty of thin oil should be used on the stone. It helps not only to pro­duce a finer cutting edge, but also to make the stone cut faster. Then too, by carrying away the waste materials, it prevents the cutting surface from becoming clogged. A very light, free-flowing oil that will not dry and gum is best. Pike oil is recommended, but kerosene mixed with a lightweight machine oil may be used. Oilstones should never be used dry and should be cleaned and kept wet with oil when not in use. If the surface should become glazed or filled with gum, clean it with ammonia or gasoline. If it is still filled, renew the cutting sur­face by dressing. When whetting a tool, use as much of the surface of the stone as possible to prevent it from wearing unevenly. When the surface becomes hollowed out in the middle, it should be dressed flat so that straight-edged tools can he properly stoned.

Fasten the bench-type oilstone in a container so that it can be kept in place while stoning the tool. The stone might be chipped or broken if it is clamped in a vise. Truing oilstones Occasionally it becomes necessary to true the surface of an oilstone. During the whetting process the portion of the stone which comes into contact with the tool is gradually worn down, forming a concave sur­face. Tools sharpened on such a sur­face will have rounded edges. True the surface by rubbing it on some kind of abrasive material which will remove the higher portions of the stone. Any one of the following meth­ods may be used:

FIRST METHOD: Place abrasive grains, aluminum oxide, or silicon car­bide, and kerosene on a flat surface of either iron, glass, or hardwood. Rub the stone over the abrasive mix­ture until the surface is flat. Abrasive grains in sizes 24 to 36 give a satis­factory surface on most stones. Finer grains should be used for extra fine stones. (This method cuts more slow­ly than some other methods because the grains are free to move over the surface instead of being held in place against the stone.

SECOND METHOD: Mount a plain silicon-carbide brick on the bench and rub the worn oilstone on the brick until it is flat, using water to carry away the waste materials. Occasionally rub the brick with a wire brush and water to keep the surface from becoming clogged. A brick 3" x 3" x 8" with No. 24 grains and grade R is suitable for such jobs. To remove any scratches in the surface of the oilstone, tack a sheet of 1 '0 garnet paper on the flat surface of a board. Hub the stone over the abrasive, using kerosene to carry away the waste material. THIRD METHOD: Select a patch of concrete sidewalk in which the sur-face stones are rather fine and rub the oilstone on the concrete until it is flat, using a generous supply of water. When the concrete loses its sharpness, shift to another surface. This is a rather "home-spun" procedure for truing an oilstone, but it is as effective as any other method. The oilstone surface can be finished by rubbing it on garnet paper, following the procedure given in the second method. Old grinding wheels and grind­stones may be used as the abrasive for truing oilstones. Do not try to true an oilstone by holding it against a running abrasive wheel. Such prac­tice will develop excessive friction and heat and cause the oilstone to break.

To repair broken stones Broken stones can be restored to usefulness by the following method: 1. Heat the broken pieces over a hot plate or other heating unit. This will drive excess oil from the inside of the stone. 2. Scrub and clean the broken edges with gasoline or cleaning solvent. 3. Match the pieces together for trial fit. 4. When the fit is satisfactory, dust the broken edges thickly with finely ground stick shellac. 5. Match the edges carefully and reheat to melt the shellac. 6. Press the pieces tightly together, using a wooden clamp or vise. 7. Dress the flat surface if the joint is uneven.