and the former then used as a pattern from which castings are obtained. In such a case the wood pattern should be made much larger than the finished articles, to be subsequently produced, are required. This is to allow for the double shrinkage, and for the dressing of the cast work. Sometimes patterns must have pegs of wire attached to enable the caster to lift them easily out of the sand. Besides wood and metal, casting patterns are often made of clay, plaster of Paris, or wax.

Moulding-sand is kept in position by means of shallow

A

FIG. 25.

B

iron frames, open at top and bottom, and called flasks. These are of various sizes, each side of a frame having a depth of about 3 inches. A flask consists of two

parts, as represented in Fig. 25, where A is the upper and B the lower frame; or they may be termed the peg-side and the eye-side respectively. In addition to the two parts shown in the figure, a third frame is often used, termed the odd-side, which is subsequently described.

§ 58. To make the odd-side.-The sand is first tempered with water, and passed through a rough sieve with about five meshes to the linear inch. It should be noted here that black or old sand does not hold together so well as raw sand, the black sand containing burnt flour, charcoal, and brick-dust; and probably the sharp edges of the particles of sand are partly worn off by frequent use, and cannot be wedged so firmly together. If black sand only be used the castings are liable to be blown, the material not being sufficiently porous to allow the air and other gases to escape.

The moulding is commenced by placing one of the frames, often termed the she-side, on the top of a flat board, then dusting the inside with parting sand, then adding some raw

sand, and filling up with black sand.

The sand is rammed

down tightly with the palms of the hands, then with the knuckles, and finished with a mallet. The surface is next scraped level with a straight-edged piece of wood, a board placed on the top, and the whole frame with its contents inverted.

The patterns are now carefully laid on the mould and the dust bag shook over them; this will leave a clear outline of the patterns upon the sand, which is then cut away in order to let them in half-way. The "odd-side," which is always the "peg-side," is now fixed to the lower frame, parting sand added, and then a mixture of raw sand and black sand, and finally black sand to complete the mould as before. The facing-sand, which is sometimes mixed with black sand, half and half, must be pounded in a mortar and passed through the meshes of a fine sieve. The odd-side must be rammed down as tightly as possible, as upon the compactness of the sand the future success of the operations depends. A board is then placed on the top and the "flask" turned over. The board which now forms the top is hammered to loosen the patterns, and the "she-side" taken off and broken up. The "odd-side" contains the patterns, and is now ready to mould from. A frame is fixed to the "odd-side," sand pressed in as before, then covered with a board, and the whole inverted. The patterns are then loosened by hammering the top board, and the odd-side, which now contains perfect impressions of half of each of the patterns, is removed, leaving the patterns in the she-side. A frame containing pegs is now fixed to the she-side, sand added and pressed as before. This peg-side is then removed and placed aside, leaving the patterns in the "she-side." The "odd-side " is then placed on the "she-side," the flask again inverted, the patterns loosened with the hammer, and the she-side removed, leaving the patterns in the "odd-side" ready to start again. It will thus be seen that the "odd-side" is used over and over again to make other moulds from, a group of five to six moulds constituting a heat. About six

heats of common brass work would be considered a fair day's work. The number of moulds constituting a heat is regulated, however, by the size of the crucibles and weight of the castings.

Before the molten metal is poured in, the impressions from the patterns in the sand must be connected by the principal ingates or channels by which the metal is run into the mould, the sand being scooped out by a special tool, termed a "drawer." This operation, although apparently simple, really requires much judgment and experience, especially in large work, in order to obtain the requisite amount of metal to feed the impressions. The runners are generally made on the "she-side," but sometimes they are employed on both the "she-side" and "peg-side." The cores are generally laid in the peg-side. For common work the metal is poured into the moulds while in the damp state, the impressions having been previously dusted with flour or charcoal.

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§ 59. Fine Work.-For fine castings the moulds, after being made, are dried before a fire, previous to dusting, and then dusted with powdered charcoal. For single-face only one side of the mould is dried. For very delicate work the face of the mould is smoked with a torch composed of pitch. In this case, after drying and torching, the moulds must be again brought in contact with the patterns before being screwed up, and the soot being in a very finely-divided state, the impression is brought out clear and sharp. The caster uses a clayey sand, termed "loam," to mix with his ordinary sand for fine work, and for that reason the moulds must be well dried. By the use of loam the chased and sharp corners of the impressions hold together better. When loam is used facing sand is necessary, and this being of a more porous nature than loam sand, permits the gases more freely to escape when pouring, and thus prevents blowholes in the work.

When moulding thin scrolls, or when the pattern has a

thin part, the moulds must not be rammed too hard, for, as the metal contracts on cooling, if the sand does not give way the metal will crack and the castings become what is termed seared. The caster overcomes this difficulty by damping the thin part of the impression with charcoal and water, which renders that part of the mould soft and yielding when the metal cools.

§ 60. Cores. When the objects to be cast are required to be hollow, they are then "cored," as it is termed. It is advisable in all cases, wherever possible, to allow the pattern to deliver its own core. This can be done by making the pattern to "leave" half-way, or by turning it taper all through. For example, in Fig. 26 a to c, the light shaded

B

d

FIG. 26.

portion marked d represents the core. In many cases this method cannot be adopted. Sometimes the pattern is moulded as though for a solid casting, and the sand core pushed out of the pattern, and fixed on the face of the mould with a splint of wood or a nail, before pouring in the metal. For many articles core-prints have to be made on the pattern, and these imprint in the mould the places where the ends of the core will subsequently be supported. The core bearing must always be of the same diameter as the prints in the pattern.

Core-stocks. These are core-boxes, generally made of plaster of Paris or wood, the interior of which contains a cavity, of the desired shape of the interior of the object to be cast. Core-stocks are made as follows: The core-bearing is placed half-way in the sand, and pieces of metal or wood placed round to form an enclosure. Plaster of Paris is then

poured over the bearing in this enclosure, and left until it has completely set. The plaster cast along with the bearing is then removed from the sand, trimmed up, and hollows cut out of the sides, and left to dry, when the bearing becomes loose. This forms one-half of the core-box. The plaster cast is then well oiled, placed in sand, an enclosure made as before, and plaster of Paris poured in. When the whole is set and dry the two parts are separated, and the bearing removed. The core-stocks are then ready for use. Should

[

any difficulty be experienced in getting the parts asunder, the stocks are placed in an oven and heated, when the parts are readily separated. These stocks are then generally used to cast from in brass or iron, so as to form permanent core-boxes.

In casting from a pattern which has a hole at one end only, the core requires to be balanced—that is, it must be heavier at one end than at the other, the light end projecting into the part which is to be hollow. Very often the core is balanced in the middle, one core being made to do duty for two castings. This principle is taken advantage of in patterns which are undercut, as in the flange of a pulley. This process is called false coring.

§ 61. Figure Casting, etc.-This most complex part of the founders' art is done by the false-coring process, the patterns being generally solid. The figure to be cast is laid as far into the sand as will enable it to leave properly, and when the caster comes to an undercut part, he dusts it with parting sand, and fits in a piece of sand. When he comes to another undercut part he uses more parting sand, and rams more sand in as before. In this way piece after piece is successively laid on the pattern, until he comes to a part which will leave the sand without breaking any portion of it. This part is then moulded, removed, and each separate piece of core taken out with two needles, in order to remove the pattern. The moulds and pieces of core have to be dried and carefully replaced, and mended if required. The im