Files and most common abrading tools are the file and the rasp, the former being used for metal and the latter for wood, horn, and other fibrous materials. These tools, especially the file, exist in almost endless variety in length, contour, thickness, and style and fineness of cut. The file and the rasp, like the grindstone and the emery-wheel, are used to remove projections and rough portions from metallic objects in order to bring them to a desired smoothness of surface and to required dimensions. The emery- and corundum-wheels and the grindstone may be regarded as rotary files driven by power. It is not deemed advisable to give here an itemized description of all the varieties and types of rasps and files, as it would be but a mere catalogue of no special interest. Figures i and 2 (j5/. 19) represent various types of files.
aid in properly holding objects which are being filed and ground there are employed various kinds of vises, both hand and bench (figs. 3, 4). The bench-vise is so called because it is fastened to the work bench. Bench-vises are of two general classes, (i) those having a hinge, and (2) those with a parallel movement; the jaws are moved and held either by a screw or by a ratchet and clamping device. For filing and grinding these vises are generally of cast iron; for chipping they are principally of wrought iron.
sharpening small tools, such as knives, chisels, etc., there is used a stationary hone or oil-stone having a fiat abrasive surface, over which is moved the material to be ground. Gouges have their con cave edges worked by slip-stones having preferably concave edges of the same radius of curvature as the cutting-edge of the tool.
the article to be ground is large, as in the case of a scythe, a paper-cutter blade, a planer-knife, a saw-blade in process of man ufacture, or a casting having its skin and sprues worked off, it is best to have the stone in the form of a disc, which, according to the size of the piece to be worked, may be revolved by hand-power, a foot-treadle, or a belt.
Mc —Perhaps the stones of grinding-mills, as in revolving they wore each other away, suggested the use of the grindstone, which is one of the oldest tools used for changing the shape of metallic objects. It acts in the removal of numberless small particles, and is employed not only to change an original shape and outline, but also to give a polish. It is mounted upon a shaft, which passes through a square hole in the stone, and which was originally carried in boxes on a wooden frame, for which subsequently an iron frame was substituted. At present the stones, par ticularly if large, are held in place on the arbor by and between cast-iron flanges, which are slightly concave on their inner sides. Such stones run from t inch to 6 feet in diameter and from of an inch to IS inches face. Most of the grindstones used in the United States come from Yorkshire, England. There are known and used many varieties of grit, which differ in the size and sharpness of the grains and the hardness of the matrix by which they are held together. The simplest form of grindstone was mounted in a very crude wooden frame, and was kept wet by a drip from a keg or a can suspended above the stone. Subsequently the stone was
revolved in a movable trough filled with water. The trough and the frame are now generally made of cast iron in one piece, while the mounting is so improved that the arbor runs on anti-friction rollers. Figure 7 (pi. 19) shows an ordinary grindstone-mounting. One excellent form of portable grindstone-frame is made in a solid casting of box form with two divisions, one for the water in which the stone turns and the other for clean water for cleansing tools. There is an outlet for the discharge of the deposit and a steady rest for grinding small toolg. The grindstone, how ever, is being very generally superseded by the emery- and corundum wheels, whose advantages are that their particles are naturally harder, their cutting-edges are not water-worn as with sandstone, the grains in any one wheel are all of a size, the softness of the matrix may be chosen to suit the work to be done, and, furthermore, they may be produced at very reasonable rates in an almost infinite variety of size and of profile.
Emery-wherls(A-.S),which are practically artificial grindstones, are used to supplement the lathe and the planer in producing true cylindrical or plane surfaces. There has never been made a lathe that will turn truly round, nor a planer that will plane truly flat. In the latter respect the emery wheel produces work of a trueness and finish which equals the best pro duced by the more expensive method of scraping and fitting upon planes, and which cannot be produced by lathe- and hand-work. Emerv-wheels are now very largely used for grinding the treads of "chilled" car-wheels. For the production of perfectly cylindrical surfaces, as for car-brasses, an emery-wheel with semicircular convex rim does excellent work at a very rapid rate. The brasses are fed along under the machine, which, if they are well moulded, will grind them at the rate of one per minute from the rough to a correct fit, leaving them with a fine finish. An emery-wheel to be of maximum service should be safe from bursting, should cut freely with but little heat, should be reasonably durable, as far as possible should be free from noxious dust and from unpleasant smell, should be of even density, should be of perfect profile, and should wear evenly. It should be well mounted and properly run, should be run at its most efficient speed as determined by practice and recommended by its maker, and should not have the work forced up against it too hard. No emerv-wheel will run well if allowed to jump. A good rim-speed is about 550o feet per minute. As a rule, an emery-wheel will remove in the same number of hours from twelve to fifteen times as much metal as a file. Emery-wheels are " turned " by a diamond-pointed tool consisting of a crystal of boart or black diamond firmly set in the end of a steel rod and furnished with a suitable wooden handle, or the boart may be mounted in a square rod and used as a lathe-tool.