The second plan devised was to put a series of small rollers one above another, with the usual spur gear on their axes, which would give every suc ceeding roller an opposite rotation, so that the bar might enter between the first and second roller, go back through the second and third roller, then through the third and fourth, the fourth and fifth, and so on to comple tion. In the annexed, Fig. 2 affbrds a side elevation, and Fig. 3, on the follow ing page, a vertical section of six small rolls, abcdef, which, by their arrange ment, are in elect five pairs. In Fig. 3 the letters gbik 1, show the situation of five shelves, (the proportionate length of which cannot be shown,) on which the iron slides; and the arrows in the same figure indicate the course taken by the bar through all the rolls. The ehelfg is supposed to be upon a level or some what lower than the mouth of the fur nace, the bloom from which is to be elided down upon g, and pushed between the rollers a and b, and as it passes out of these, it gradually bends down, the end falling in the position of the arrow at h, ready to enter between the rollers b and c; thenupon i between c and d, upon k between d and e, upon 1 between e and f, and so on to any num ber of rolls underneath, or be conducted forward to another series of rollers placed before it. Both the plans now described may be employed separately or jointly ; but for various reasons the vertical series would be preferable for roughing the work, while the hori zontal arrangement would probably be best suited for finishing the work. It ' is to be understood that the foregoing diagrams are only designed as explana tory of the principle of construction, all the subordinate details being omitted as unnecessary in this place. Previous to the year 1829, the writer had never seen nor heard of iron being rolled on either of the plans described ; he had seen several iron works, one newly built, in none of which, however, was the principle adopted ; he could find no published account of any thing of the kind ; his mechanical friends said the plans were new and valuable, and a patent was determined upon if the opinions of two or three respectable iron masters, whom he consulted, should be favourable ; when, singular to relate, two of these persons, who had very exten sive concerns, condemned the plans as useless and impracticable, while the third said they were not only practicable, but highly advantageous ; and he proved the truth of his assertions by showing the writer his works, wherein iron was at that time being rolled on the very principle of both plans, where he was informed it had been practised for several years ; and that similar rolls were used in several of the works of Staffordshire! This fact has been men tioned with the view of inculcating circumspection in inventors before they incur the expense of patents, and a disregard of dogmatical opinions when unsupported by reason. It is worthy of remark in this place, that in none of the recent treatises on the iron manufacture has any notice been taken of this important improvement in rolling iron. The plan at the iron works where the writer saw the principle in operation, is a modification of that which has been described; it consists of only three rolls one above another, but of the same kind as those delineated at page 775, so that a bar which has passed through a groove between the top and middle roll is sent back through another groove between the middle and lowest roll ; and there being many grooves in each of the three rolls, they are thus passed alternately through the upper and lower range of grooves until completed : but in making vat hoops, the bar, after being passed through several grooves, to roll it to a thin, yet rough flat bar, proceeded onward, horizontally (in the same manner as shown in the diagram, page 776), and entered between a pair of plain polished rolls, where it was reduced to the required thinness, and a smooth face was given to it.
Horton's mode of rolling large Bars.—For bars of still greater dimensions Mr. Horton adopted the following process, for which he took out a patent a few years back. Instead of rolling the single blooms, and then welding the bars toge ther, to get bars of the sizes required, he takes the blooms (" billets," he calls them,) from the puddling furnace, welds several of them together under the great hammer, then submits the united mass to the operation of the rolls. Great bars, thus prepared are said to possess a more laminated and fibrous texture lon gitudinally, than those which are united by welding together ready formed bars.
The various Forms of rolled Iron.—Having seen that round iron is produced by the junction of two semicircular grooves in the opposite rollers, the reader will readily perceive, without the aid of a figure, that "half-round iron," (that is, semicircular in its transverse section,) will be produced by having only one roller with a semicircular groove, and the opposite roller with no groove at all; and that, by making the groove of less depth, that is, of an elliptical curve, a semi-elliptical, or " half-oval " iron bar will be formed; also that by the junction of two semi-elliptical grooves, " oval iron " will be the result. The two last mentioned sorts are extensively used by coach smiths ; also for the tope of fenders, wire-guards, and such like. It will likewise be evident to the reader,
that as square iron is made by two angular grooves, one of such grooves opposed to a plain roller will produce triangular, or " three-square iron ;" that as flat bars are made by grooves of this form —, it will be only necessary to make the opposite groove deep and narrow, thus I, and let the latter groove come next to one end of the former, to produce L or "angle-iron." This angle-iron, though of recent introduction, is, on account of its very great utility in making framing, cases, boilers, and a thousand other things, a great favourite with all kinds of smiths, as it enables them to execute superior work with much less labour. Seeing how the angle-iron is made, it will be readily understood that, by planing this i groove so as to come in the middle of this groove in the opposite roll, that "T iron" will thereby be rolled; and this brings us to a clear understanding bow "railway-iron" is made, as the form is usually but a slight modification of the T, by a little rounding of some of the parts; and by obvious combinations of the foregoing, it will be seen how "iron mouldings,' of an infinite variety, may be produced by a pair of rolls, and with far more facility and dispatch than a joiner can make them of wood with his moulding planes.
Slit Rods.—The manufacture of this article is interesting from the wonderful rapidity of its execution ; and that it is of great importance in its results, it need only be stated that in the neighbourhood of Birmingham alone, it furnishes the highly-convenient raw material to upwards of sixty thousand people, men, women, and children, who are employed in nail-making, besides being applied to an infinite variety of other purposes. The slitting is performed by what we would define to be a series of circular shears, formed by the continued contact of a pair of deeply-grooved steeled rollers, which cut by the intersection of their angular edges, as will be clearly understood by reference to the subjoined engraving, which exhibits a pair of slitting rolls, adapted to slit a flat bar or slab, of about seven inches wide, into thirteen equal parts. An end view of this slab is intended to be represented at a, and by presenting it between the two rolls at b b it is obvious that the edges, as they inter sect each other in their revolution, will divide the slab in the manner shown at a, and force them into the cavities between theni, in which manner they will pass out of the rolls in a finished state, requiring only to be tied up into bundles afterwards, of the usual weight of 56 lbs. To faci litate the operation of slitting, the bar passes from the rolls where it has been formed of the required dimensions,- in its red-hot state, directly between the slitters. In this manner upwards of thirty rods, of a small size, axe made at once by a single revolution of a pair of rolls. As the sizes and forms of the rods required are extremely various, it is necessary in a slitting mill to have, at the least, two pair of rolls for each size, that a freshly-turned pair may be in readiness to supply the place of those which become worn or damaged. Slit rods are always more or less ragged at their edges, but this is of trifling import compared to the advantage of their great cheapness, especially in the making of nails, where they have to be drawn out under the hammer. To prevent any considerable burr, or ruggedness of edge in the rods, the slitting rolls are turned with great care and truth, so as accurately to fit each other Rog of Plate or Sheet Iron is performed between perfectly plain rolls, as before mentioned, for hoops; but the rolls are necessarily of greater dimensions, frequently as wide as five feet; and of course a very great power is required to compress at once so extensive a line of surface. For ordinary sheet iron, such as is called " double and single plate," only one pair of rolls is employed at a time, the rolls being set nearer together by regulating screws, each suc ceeding time that a sheet is passed through. In rolling boiler plates, which are often more than half an inch in thickness, and weigh more than 2 cwt. each, the manual labour is very severe. The iron for these plates is prepared by making a pile of rough bars, which is heated in an air furnace, and then subjected to the action of the great forge hammer, already described, which reduces the pile to a thick slab, the forgers moving it under the hammer, so as to give it somewhat of the figure, as to length and breadth, required for the finished boiler plate. It is then heated again in the furnace, and rolled to the required thickness by repeatedly passing the plate between the rolls, the rollers adjusting the rolls nearer together each succeeding time, and taking due care to present the plate in such positions as will extend it to the required shape and dimensions, sometimes making it enter the rolls corner ways, sometimes length ways, and sometimes breadth ways; the skill and efforts of the workman being directed to bringing the plate to the required form and dimensions at one heat, and so as to require but very little superfluous edging to be subsequently taken off by the shears.