TRON-FOUNDERY, the art of casting 1 iron, and forming moulds, into which it is poured when in a fluid state.
The moulds are commonly made in sand, held in wooden frames, (fig. 3 and 4, Plate Iron-foundery.) Two of these frames, A B, (fig. 4.) are called a pair of flasks, and fit together by pins, a a, in one flask, entering eyes, b b, in the other. A wooden pattern of whatever is to be cast must first be made, exactly of the same dimensions as the article required. For an example, we have chosen to describe the manner of casting a roller, such as is used for the wheels of small waggons, the rolls of windmill heads, &c. The pat tern is shown in fig. 5, 6, and 7: fig. 51s a plan, fig. 6 a section, and in fig. 7 it is shewn edgeways. This pattern is exact ly similar to the wheel which is to be cast, except that, in place of the hole through the centre of the wheel, a pin, m, is stuck on, projecting from each side in the same place that the holes will be : the use of these pins will be shown hereafter. The lower flask, A, (fig. 4.) is placed on a board laid on the ground; it is then filled with sand, and rammed down, first with the rammer, (fig. 9) and afterwards with fig. 10, which is broader, and smooths the work. The workman then with the trow el, (fig. 8) digs out a hole in the sand, and presses the pattern into it, the flat surface horizontal, and fills the sand in round the pattern, until it is exactly half buried ; he then takes out the pattern, and if there are any holes in the under part, where the sand is not fillea round close to the pattern, he puts in a small quantity of sand, and presses the pattern down again, until a perfect impression of it is left in the sand, as in fig. 1. Ile now returns the pattern, and sprinkles some dry sand, which has been burnt in the furnace, over the pattern and flask, and then places the upper flask, B, (fig. 4) upon it : two small sticks are placed upon the pattern, and the sand filled in round them ; the sand is rammed down by the rammers (fig. 9 and 10), and the two
sticks drawn out, leaving holes, 11, (fig. 2) through the sand in the upper flask.— The workman now takes off the upper flask, II, by its two handles, leaving the pattern in the lower flask; the burnt sand causes the two flasks to separate exactly at the joining of the flasks : the upper flask is now completely finished, the holes, 11, made by drawing out the sticks, being left to pour in the metal, and the pattern leaving a perfect print of its upper half in the flask. The next operation is lifting the pattern out of the lower flask, before which the workman wets the sand around the pattern, that it may adhere to gether, and not be broken by rifting the pattern. The two pins projecting from the wheel where the hole is to be, leave their impressions in the sand, forming two holes, e f (fig. 2) one in each flask. These holes receive the ends of a core, which is exactly the shape and size of the hole required in the wheel : the core is formed of a mixture of plaster of Paris and brick dust, and is made just the length and size of the pins in the pattern, that it may be truly in the centre of the wheel. Fig. 2. is a section of the two flasks when put together ; but the core is not put in : 11 are the holes for the metal, and g h i lc the hollow cavity to receive it.
The iron is melted in a furnace, and brought from it in a ladle (fig. 11) which has three handles, and is carried by two men, the forked handle, M, giving a pur chase to the man holding it, to turn over the ladle to deliver its contents. If the work is very small, the metal is conveyed to the flasks in common ladles.
The more intricate cases of iron-found ery, as the casting of cylinders for steam engines, crooked pipes with various pas sages, &c. are cast in moulds formed of loam or clay, and are done nearly in the same manner as the moulding of plaster casts from busts, &c. but our limits will not allow us to describe these curious branch es of the founder's art.