A band of iron is forged, of two inches broad, and one inch thick. This is prepared at the great forge. About a foot in length is cut off, and heated to redness in a fire of charcoal. It is then beaten on one side with a hammer, so as to work all the surface into furrows or grooves, in order that it may retain the substance called the potin, which is to be welded upon one side of the iron, to form the hard matter on which the holes are to be pierced. This potin is nothing but fragments of old cast-iron pots; but those pots which have been worn out by the continued action of the fire, are not good; the fragments of a new pot, which has not been in the fire, are better.
"The workman breaks these pieces of pots on his anvil, and mixes the pieces with charcoal of white wood. lie put this in the forge, and heats it till it is melted into a sort of paste; and to purify it, he repeats the fusion ten or twelve times, and each time he takes it with the tongs to dip it in water." M. Du Hamel says, this is to render the matter more easy to break into pieces.
"By these repeated fusions with charcoal, the cast iron is changed, and its qualities approach those of steel, but far from becoming brittle, it will yield to the blows of the hammer, and to the punch, which is used to enlarge the holes The bar of iron which is to make the draw-plate, is covered with a layer of pieces of the potin, or cast iron thus prepared. It is applied on the side which is furrowed, and should occupy about half an inch in thickness. The whole is then wrapped up in a coarse cloth, which has been dipped in clay and water, mixed up as thick as cream, and is put into the forge. The potin is more fusible than the forged iron, so that it will melt. The plate is withdrawn from the fire occasionally, and hammered very gently upon the potin, to weld, and in some measure amalgamate it with the iron, which cannot be done at once; but it must be repeatedly heated and worked, until the potin fixes to the iron. The workman then throws dry powdered clay upon it, in order, they say, to soften the potin.
"The union being complete, the plate is again heated, and forged by two work men, who draw out the plate of one foot to a length of two feet, and give it the form it is to have. It is well known, that cast iron cannot be worked at the forge without breaking under the hammer; but in the present instance, it is alloyed with the iron-bar, and is drawn out with it. It has also acquired new properties by the repeated fusions with charcoal.
"The holes are next pierced whilst the plate is hot. This is done with a well-pointed punch of German steel, applied on that side of the plate which is the iron-bar. It requires four heats in the fire to punch the holes, and every turn a finer punch is employed, so as to make a taper hole. The makers of draw-plates do not pierce the holes quite through, but leave it to the wire-drawers to do it themselves when the plate is cold, with sharp punches, and then they open the hole to the size they desire; and although this potin is of a very hard substance, the size of the hole may be reduced by gentle blows with a hard hammer, on the flat surface of the plate round the hole.
"A great many holes are made in the same plate; and it is important that they should diminish in size by very imperceptible gradations; so that the workman can always choose a hole suitable for the wire he is to draw, without being obliged to reduce it too much at once."
The next considerable wire manufactory in France, and probably in the world, is that of the Messrs. Mouchel, situated at L'Aigle, in the department of L'Orne. It furnishes annually in cards, for wool-combing only, 100,000 quintals of iron-wire = 10 millions of pounds! The whole of this is not required for home consumption, but is exported to Spain, Portugal, Italy, and other countries. As the excellence of their products is in a great measure attributable to the perfection of their draw-plates, we shall here add the process of preparing them, as described by the Messrs. Mouchel, which differs from that previously explained.
"Several pieces of iron are disposed in the furnace, in the form of a box without a lid, their weight being according to the use for which they are intended to be made. The workman fills each of these boxes with cast steel, and having covered it over with a luting of clay, it is exposed to a fierce fire until the steel be melted. His art consists in seizing the proper moment to withdraw the plate from the fire; he raises the luting, and blows on it through a tube, in order to drive off all heterogeneous parts, and then amalgamates it with the iron by light blows; after it is cool, he replaces it at the fire, where the fusion again takes place, but to a less degree than before; he afterwards works the steel with light blows of the hammer, to purify and solder it with the iron. This operation is repeated from seven to ten times, according to its quality, which renders it more or less difficult to manage. During this process, a crust forms on the steel, which is detached from it the fifth time of its exposure to the fire, because this crust is composed of an oxidated steel, of an inferior quality.
It sometimes happens that two, and even three, of these crusts are formed of about two millimetres, or one-sixteenth of an inch, in thickness, which must also be removed.
"After all these different fusions, the plate is beaten by a hammer wetted with water, and the proper length, breadth, and thickness, are given to it. When thus prepared, the plates are heated again, in order to be pierced with holes by punches of a conical form; the operation is repeated five or six times, and the punches used each time, are progressively smaller. It is of importance that the plate never be heated beyond a cherry-red, because if it receives a higher degree of heat, the steel undergoes an unfavourable change. The plates, when finished, present a very hard material, which nevertheless will yield to the strokes of the punches and hammer, which they require when the holes become too much enlarged by the frequent passing of the wire through them.