Metal plate

“ The plate was now carefully heated over a charcoal fire, fresh amalgam being added, as the powder fused, upon any defective places. When the powder had become thoroughly liquid, so as to fill all the lines, the plate was allowed to cool, and the whole surface was scraped, so as to remove the superfluous niello, leaving only what had sunk into and filled up the engraved pattern. Last of all the nielloed plate was very highly polished, till it presented the appearance of a smooth metal surface enriched with a delicate design in fine grey-black lines. ”

“ The length of time it remains in the pot depends upon the heat of the metal, but it is generally from ten to fifteen minutes, when it is taken out, and put aside to cool. On opening the pan, nothing is seen but a solid lump of metal, which, when carefully broke round the mould, a thin plate is obtained from the mass, exhibiting a perfect appearance of the page from which the mould was taken.—This is called a stereotype plate, which in general is not above the eighth of an inch thick, and is printed from in the same manner as a page of types. ”

“ Then it is hung over a flat cauldron filled with melted type-metal, and lowered to rest in it. When the plate has acquired the same degree of temperature as the metal, the latter is ladled and poured over the plate, filling up all the hollows and indentations, and forming a solid back of lead.257 The coating of tin is first applied, as lead will not adhere to copper.
The plate, being now ready for the planing, beveling, picking, and correcting of stereotype plates, goes through the same process that we have before described. ”

“ An inking plate may be made from a hard, rigid, scratch-resistant metal plate 6 inches wide by 14 inches long or by inlaying a block of wood with a piece of glass one-fourth of an inch thick, 6 inches wide, and 14 inches long. ”

“ These stripping plates are of metal, but in order to save the cost of filing them in iron or steel, many are cheaply made by casting a white metal alloy round the actual pattern itself in the first place, the white metal being enclosed and retained in a plain iron frame which forms the body of the plate. Lastly, many machines, but not the majority, include provision for mechanically ramming the sand around the pattern by power instead of by hand. This is really the least valuable feature of a moulding machine, because it is not applicable to any but rather shallow moulds. ”

“ What is called French plate is made by heating copper, or more frequently, brass, to a certain degree, then applying leaf-silver to the surface, and strongly rubbing it with a burnisher. The durability of this plating depends of course on the number of leaves which are applied on a given surface. For ornaments that are not much used ten leaves may be sufficient; but a hundred will not last long, if the metal be exposed to frequent handling or washing. ”

“ The metal is easily raised to take the proper design, by a very careful application of the hammering process.
Sometimes in silver-working the form of the object to be manufactured is of such a nature as not to allow of the use of the swage tool, and this is more particularly the case in the manufacture of plate. ”

“ The different metals are malleable, ductile and tenacious in the following order; white metal or britannia, aluminum, zinc, copper, low brass, high brass, German silver, steel, tin plate. White metal does not harden in spinning, but it requires special skill in handling, or the metal will be of very uneven gage. The best metal for an amateur to start on is copper, as it is both tenacious and ductile, and will stand much abuse in the fire and on the lathe. ”

“ The shape of the surface plate is an element of the first importance, because as even the strongest bars of metal deflect from their own weight, it is necessary to shape the plate with a view to make this deflection as small as possible in any given size and weight of plate. ”

“ When an oblong lump of metal is forced through a series of progressively diminishing apertures in a steel plate, so as to assume in its cross section the form and dimensions of the last hole, and to be augmented in length at the expense of its thickness, it is said to be wire-drawn. The piece of steel called the draw-plate is pierced with a regular gradation of holes, from the largest to the smallest; and the machine for overcoming the lateral adhesion of the metallic particles to one another, is called the draw-bench. ”

“ Various gold twists and cords can be obtained; they are composed of several threads twisted up in the usual cord fashion, each ply consisting of gold spun round a silk thread.
Plate is a flat strip of metal commonly about one-sixteenth of an inch wide; it can be obtained in different widths.
Spangles.—These are small variously shaped pieces of thin metal, usually pierced with a hole in the centre for fixing on to the material. They are frequently circular in shape, and either flat or slightly concave ”

“ CHAPTER VI. METAL SPINNING. Spinning sheet metal into various forms is another kind of work which can be done in the foot lathe, and it is here that the amateur can show his taste and dexterity.
The process consists in forming a blank, like this engraving, into an ornamental base for a lamp, or an oil cup; in fact, any thing whatsoever. All that is requisite is to have a fac simile, in wood, of the shape you wish to make. This is bolted or otherwise made fast to the face plate, and the blank is then set up against it, and held as the cylinder head, shown in Fig. ”

“ The patent fittings remedy this, and save both time and trouble; in place of the rows of holes so far apart, metal strips perforated at intervals of three-quarters of an inch for the reception of the very simple but strong metal plates, which take the place of the old studs, are mortised in and screwed to the frames. ”

“ So, in recent times, researches have been making upon the efficacy of armor plating, no longer in its exaggeration of thickness, but in the intrinsic quality of the metal of which it is composed. Metallurgists have applied themselves to the work and have thus brought out various products, among which the plates called "compound," of Messrs. Cammell & Co., have obtained a great notoriety. These plates, formed of a true plating of steel upon a bed of soft iron, have been much in vogue in the English navy, and seemed as if they were to be adopted about everywhere. ”

“ MOCK GOLD Fuse together 16 parts of copper, 7 of platinum, and 1 of zinc. When steel is alloyed with 1/500 part of platinum, or with 1/500 part of silver, it is rendered much harder, more malleable, and better adapted for all kinds of cutting instruments. Note.—In making alloys, care must be taken to have the more infusible metals melted first, and afterwards add the others.
151. BRITANNIA METAL Take 4 parts of brass, and 4 parts of tin; when fused add 4 parts of metallic bismuth, and 4 parts of metallic antimony. ”

“ The edges are cut by a circular saw and trimmed by machine-tools, and the plate is rendered perfectly even, and adjusted with the greatest possible exactness to the required thickness. It is prepared for the press by being screwed down upon a block of wood of a certain thickness, so that the face of the plate may have the same height as common type, the screws passing through the margin or other hollow parts of the face of the cast. No more enduring surface than the copper of these electrotype casts, backed up by the hard alloy, has yet been discovered. ”

“ A brief description of the proper method will still further illustrate the case already considered, and will also show how surface plates are to be corrected.
Take three plates of cast iron, of equal size and proportionate strength. The metal should be of a hard quality. The plates should be well ribbed on the back to prevent them from springing, and each of them should have three projecting points on which to rest, placed triangularly in the most favourable positions for bearing. ”

“ A good type-foundry is always provided with several furnaces, each surmounted with an iron pot containing the melted alloy, of 3 parts of lead and 1 of antimony. Into this pot the founder dips the very small iron ladle, to lift merely as much metal as will cast a single letter at a time. Having poured in the metal with his right hand, and returned the ladle to the melting-pot, the founder throws up his left hand, which holds the mould, above his head, with a sudden jerk, supporting it with his right hand. It is this movement which forces the metal into all the interstices of the matrix ”

“ A large number of thin plates of various metals, gold, silver, copper, together with alloys of different metals are soldered together in a particular order, a pattern is hammered into the soldered edges, and the whole is hammered or rolled into a single thin plate, the pattern then appearing in the order in which the various metals were placed. ”

“ A metallic alloy is made of tin, lead, bismuth, and antimony, which melts at a moderate heat. This is poured into the sheet-iron tray, and after it is cooled and concreted, it is inverted, and shaken off from the model bars, so as to form a mass of metal perforated throughout with tubular cavities, corresponding to the intended pencil-pieces. The paste is introduced by pressure into these cavities, and set aside to dry slowly. When nearly dry, the pieces get so much shrunk that they may be readily turned out of the moulds upon a cloth table. ”

“ Steel plates, being rolled from a nearly homogeneous ingot, have nearly the same strength in both directions, provided the process of rolling is completed at a temperature high enough to allow recrystallization to take place in cooling. Cold-rolled or cold-drawn metal is not isotropic because the crystals of which it is made up have been elongated in one direction by the process: but isotropy may be restored by heating the piece sufficiently to allow the crystals to re-form. ”

“ Upon analysis the brass was found to contain 70%-75% copper, 20%-30% zinc, and other trace elements. The blades, cocking levers, and button releases of lancets and scarificators were found to be made of ferrous metal (iron or steel) . In addition to the typical brass pieces, a number of “white metal” pieces were analyzed. (The term “white metal” is used to designate any undetermined silver-colored metal alloy.) Those white metal pieces dating from the eighteenth century (a Swiss or Tyrolean fleam and an English veterinary spring lancet) were found to be composed entirely of ferrous metal. ”

“ Rocking in from forty to sixty directions is necessary to cover the plate properly. The durability of a mezzotint plate depends entirely upon the pressure put upon the rocker, and the depth to which it penetrates the copper. After the ground is thus laid, the outline is sketched in on the rocked surface, which takes the pencil easily, and then with steel scrapers and burnishers the light and middle tints are worked down, leaving undisturbed the portions of the surface where the strongest blacks are to be. ”

“ But in those forms where curving must take place in different directions the layers or fibres of metal are made to glide over one another, extension taking place in some layers but not in others, and this goes on without producing much reduction in the thickness. This is only possible with malleable and ductile metals and alloys. As a general rule it is restricted to metals which are not cast, for, with some slight exceptions, it is impossible to produce relative movements of the layers in cast iron, steel or cast brass. ”

“ The metals thus united may be either the same or dissimilar; but the uniting metal must always have an affinity for both. Solders must be, therefore, selected in reference to their appropriate metals. Thus tin-plates are soldered with an alloy consisting of from 1 to 2 parts of tin, with 1 of lead; pewter is soldered with a more fusible alloy, containing a certain proportion of bismuth added to the lead and tin; iron, copper, and brass are soldered with spelter, an alloy of zinc and copper, in nearly equal parts ”

“ It must be cast of hard and close-grained iron, which will possess the most durable qualities, in a baked mold without a cope, so that the gas shall escape most freely. As cast, the plate should be one inch thick. About three eighths of an inch is planed off, [234] removing all dirt, and leaving a perfectly sound surface, with a thickness of about five eighths of an inch. Three of these plates are made. After these have been planed, their edges squared and steel handles put in they are delivered to the fitter. ”

“ The plates are prepared for the engraver from sheets of steel about one-sixth of an inch in thickness. A plate cut from a sheet of this kind is first softened by heating it with charcoal, and suffering it to cool gradually in the atmosphere. It is next planished, or hammered on a peculiar kind of anvil, to make it perfectly level, and afterwards ground on one side upon a grindstone. The operation is completed by polishing it with Scotch stone and charcoal. When steel was first substituted for copper, it was hardened before it was used in printing ”

“ Next prepare the metal holder. This may be made of brass or copper and need not be of very heavy gauge-No. 22 is plenty heavy enough. The easiest way to get the shape of the metal is to make a paper pattern of the development. The illustration shows how this will look and the size of the parts for the back dimensioned above. Trace this shape on the metal with the carbon paper and cut it out by means of metal shears. Polish the metal, using powdered pumice and lye, then with a nail, punch the holes, through which small round-head brass screws are to be placed to hold the metal to the wood back. ”