In this simple yet elegant arrangement, time is also the measure of the particles respectively deposited in the 12 or more vessels, their number being determined by the quantity of sizes respectively required in the manufacture to which the emery is applied. When the vessels are to a certain degree filled with emery, the process is stopped, they are emptied, the emery is carefully dried and laid by, and the process is recommenced.
6. - Emery Paper is prepared like glass paper, and of about six degrees of coarseness. The powders sifted through the sieves with 30 and 90 meshes per linear inch being in general the coarsest and finest sizes employed. When used by artizans, the emery paper is commonly wrapped around a file or a slip of wood, and applied just like a file, with or without oil, according to circumstances. The emery paper cuts more smoothly with oil, but leaves the work dull.
7. - Emery Cloth only differs from emery paper in the employment of thin cotton cloth instead of paper, as the material upon which the emery is fixed by means of glue. The emery cloth, when folded around a file, does not ply so readily to it as emery paper, and is apt to unroll, therefore smiths, engineers and others, give the preference to the emery paper and emery sticks; but for household and other purposes, where the hand alone is used, the greater durability of the cloth is advantageous. Edwards' patent for emery cloth was taken out in December 1830.
8. - Emery Sticks, are rods of deal about 8 to 12 inches long, planed up square, or with one side rounded like the half round file. Nails are driven into each end of the sticks as temporary handles, they are then brushed over one at a time, with thin glue, and dabbed at all parts in a heap of emery powder, and knocked on one end to shake of the excess, two coats of glue and emery are generally used. The emery sticks are much more economical than emery paper wrapped on a file, which is liable to be torn.
9. - Emery Cake consists of emery mixed with a little suet chopped small, rendered down, and mixed with a very little bees' wax, so as to constitute a solid lump, with which to dress the edges of buff and glaze wheels. The ingredients should be thoroughly incorporated by stirring the mixture whilst fluid, after which it is frequently poured into water, and thoroughly kneaded with the hands, and rolled into lumps before it has time to cool. The emery cake is sometimes applied to the wheels whilst they are revolving; but the more usual course is to stop the wheel, and rub in the emery cake by hand, it is afterwards smoothed down with the thumb.
10. - Emery Paper, or Edwards' Patent Razor Strop Paper, is a new article in which fine emery and glass are mixed with the paper pulp, and made into sheets as in making ordinary paper. The emery and glass are said to constitute together 60 per cent. of the weight of the paper, which resembles drawing paper except that it has a delicate fawn colour. This emery paper is directed to be pasted or glued upon a piece of wood, and when rubbed with a little oil to be used as a razor strop, of which it is by far the least expensive of any previously in use. The patent for this invention was granted to the Rev. Mr Edwards, in November 1843, and he was rewarded for the same by the Society of Arts, in June, 1846.
11. - Barclay's Artificial Emery Stone. - The numerous articles already given on emery, and various ways in which it is prepared and used will be concluded by a description of the invention of a Mr. Henry Barclay, who took out letters patent in August, 1842, for a very efficient mode of combining powdered emery into disks and laps of different kinds, suitable to grinding, cutting, and polishing glass, enamels, metals, and other hard substances. The process of manufacture is as follows: -
Coarse Emery Powder is mixed with about half its weight of pulverized Stourbridge loam, and a little water or other liquid, to make a thick paste, this is pressed into a metallic mould by means of a screw press, and after having been thoroughly dried, is baked or burned in a crucible, muffle, or close receiver, within a furnace, at a temperature considerably above a "red heat,'" and below the "full white heat"
In this case the clay or alumine serves as a bond, and unites the particles very completely in a solid substance, called Artiftcial Emery Stone, which cuts very greedily, and yet seems hardly to suffer perceptible wear or destruction.
Superfine Grinding Emery, is formed into wheels exactly in the same manner as the above, but the proportion of loam is then only one-fourth, instead of one-half that of the emery: these emery stones, which are of medium fineness, cut less quickly but more smoothly than the above.
Flour Emery, when manufactured into artificial stones, requires no uniting substance, but the moistened flour emery is alone forced into the metal mould and fired, as some portions of the alumine present seem abundantly to suffice to unite the remainder. These fine wheels render the works submitted to them exceedingly smooth, but they do not produce a high polish on account of the comparative coarseness of the flour emery.
Stourbridge loam is by no means the only ingredient used in uniting the particles of emery, as many other substances answer as well; such as slate, Yorkshire gritstone, crocus, etc, and in this way the hardness and cut of the emery stone may be varied to a great extent.
Most of the grinders made of the Emery stone are formed with central holes, so as to admit of being attached to the lathe upon appropriate chucks or spindles; and the substance is so porous as to absorb much water, which is gradually thrown to the surface by the centrifugal motion so as to keep the edge conveniently moist, or with excessive velocity, the water is thrown off as in trundling a mop. Mr. Barclay has made the disks of various diameters from 1/4 inch to 8 or 10 inches diameter, but the difficulty increases with the size, as the large ones are liable to warp and crack in the firing.
When the emery stone laps are required to have plane surfaces, angular or convex edges, etc, that could not be readily moulded, the composition is partially fired at a low heat, then turned in a lathe to the specific form, and the firing at a nearly white-heat completes the manufacture.
The coarse emery stone has been tried in cutting glass, and is reported then to fulfil in itself the offices, first, of the iron disk fed with sand used in roughing, and secondly, of the Lancashire fine grit stone used in smoothing; as when of proper consistence, the artificial emery stone cuts as quickly as the former, and as smoothly as the latter, and has the advantage of maintaining its form in an eminent degree.
Small fragments of these disks, spoiled in the firing, have been successfully used in scrubbing off the rough sand coat of door plates, mouldings, etc, cast in brass, etc, and indeed the Patent Emery Stone eminently deserves more extended use than it has, up to the present time, attained.
It remains to be observed that Mr. Barclay took up the subject of the Artificial Emery Stone from necessity, as in his professional employment of making artificial teeth and gums, of a kind of hard porcelain, he found the small grindstones, (tediously prepared by rubbing down waste flakes of the Yorkshire stone used for paving into flat plates, and which are afterwards drilled and turned to the requisite forms,) wore out amazingly quick, even when assisted by coarse sand and water; but the present scheme fulfils the office of the grindstone in an admirable manner; and some small artificial stones made as above have been in almost daily use for 3 or 4 years.
The project bears an evident analogy to Mr. Prosser's Patent for making buttons, various articles, and even fire bricks, out of dry clay in powder compressed in a mould and afterwards burned, and it offers certain advantages over the corundum wheels used in India, and described under the head Corundum.