BECAUSE OF ITS ABILITY TO WITHSTAND BENDING AND 180–DEGREE TWISTS IT IS OFTEN JOCULARLY REFERRED TO AS THE “RUBBER CASTING.” (FIG. C) ] Lifting the cope or top half, it is turned upside down, and, after cutting in the drag the “runner” or “gate” connecting the “sprue” hole with the casting, the halves of the pattern are carefully drawn that the sand may not be disturbed. Now in the cavity left in the drag, to make the hole in the casting, is hung the baked “core” of sand, held together by flour or rosin or a “drying” oil. The cope is carefully replaced upon the drag, thus “closing” the mold. As will be noted from the drawings, there is left between the core and the mold a space all around, which will be filled by the metal of the casting when poured. Therefore the surface of the core shapes the inside, and the mold itself the outside and ends of the casting. The molten metal, entering through the vertical “sprue” hole, flows along the “runner” and into the mold through the more or less constricted entrance called the “gate.” The gases formed during pouring and the air with which the mold was filled are driven out through the porous bodies of sand of the mold and core. Had the mold been rammed too hard the gases could not escape through the sand and an imperfect casting would result. The poured mold is allowed to stand until the metal has solidified and cooled sufficiently, when the casting is “shaken out.” The sand is returned to the molder to be used again. The sprue and runner are broken from the casting, which, after cleaning by “tumbling” with others in a revolving mill, or otherwise, goes to the machining and assembling shops. Some form of the above general method is everywhere used for the production of all kinds of castings, except for those which can be made by machine at a lower cost for molds. This kind of molding, which we have termed “hand work,” requires expert molders and is too slow and expensive for the hundreds of standard shapes and sizes of castings which are in great and constant demand. The latter are made on cleverly devised molding machines working with compressed air or by hand power applied through a lever. The pattern is attached to the machine, set and very accurately adjusted by a skilled mechanic. Thereafter the sand is rammed, the runner formed and the pattern drawn by the machine itself, all of these very critical movements being therefore rapidly and unerringly duplicatable any desired number of times by unskilled labor, which has but to put on the parts of the “flasks,” feed in the sand, set the cores, close and remove the mold, and begin the next. Sometimes there is but one, but for the smaller sizes there are often ten or twenty, and, occasionally, as many as two hundred pieces or castings in a single mold. CHAPTER XII MALLEABLE CAST IRON