Page:The American Cyclopædia (1879) Volume IV.djvu/84

 76 CASTING cheeks. A wooden flask, containing^ one cheek and having the parts fastened to'gether by clamps, is represented in fig. 6. The drag as well as the cheeks is a rectangular frame made of plank, similar to the four sides of a box without top or bottom. The cope is similarly constructed, but having in addition FIG. 6. -Moulding Flask. pro. 7. Cop. one or more bars running across it, of variable depth, to suit the shape of the mould, and into which nails are driven to assist in holding the sand. in place. Fig. 7 represents the construc- tion of a wooden cope. Iron flasks have the same general con- struction, with the ad- dition of strong ears by which they may be lifted with a crane. It is upon the proper construction and management of the flask, and the nice and exact mixing and tempering of the moulding sand, that much of the success in cast- ing depends. Indeed, the founder regards his work as chiefly accomplished when the mould is fairly dressed and faced, and proper avenues have been provided for pouring and for the es- cape of air and gases, and the cope is read- justed to its place in such a manner that no part of the surface of the mould is disturbed. In making a flask mould, the moulder first lays upon the floor what is called a turn-over board, and upon this places the pattern. If this is of such a form that it will not lie firmly, or if it is liable to be bent or broken by packing of the sand upon it, it must be supported by a bed piece. Facing sand, which is prepared by mixing fine dry sand with the ground scrapings from the surface of previous castings, is then sifted over it, and the drag is laid upon the turn-over board. Sand is then thrown in, covering the pattern to a certain depth, and packed with the hand. More is then thrown in, perhaps enough to fill the drag, and then the moulder treads it down evenly with his feet, when, taking a rammer (see fig. 8), and using the end containing the pin, he proceeds to pack it firmly all round the sides of the drag. Then, using the butt end, he rams the sand firmly all over the mould. After the drag, and whatever checks may be used, are filled, the bottom board is placed over it and clamped or keyed to the turn-over board. The pattern is thus enclosed in a box, and lying _ upon its bottom, covered with sand. The drag is then turned ovr, bringing Rammer 1 *^ ie bottom board to the bottom, and the pattern to the top. The clamps are then removed and the turn-over board is taken off, leaving one side of the pattern un- covered. With a parting trowel (a small thin- bladed tool, similar in form to a bricklayer's trowel), a joint or parting is made by scraping away some of the sand from about the pattern, and especially to the furthest lateral lines, so that it may be drawn without injury to the mould. The surface of the sand is then smooth- ly dressed, and parting sand is sifted from a bag over its surface as well as that of the pattern, and the superfluous particles are blown away by a bellows. Pieces of wood, some cylindrical and some flat, are next placed upright on the surface, to form holes for pouring and for the escape of air, which is effected by their re- moval on the completion of the mould. The air holes are sometimes made with a pin, and are above the cavity; the pouring holes are usually at the sides, and connected by horizon- tal channels. Fine moulding sand is now sifted over to a sufficient depth to insure a smooth surface, and the cope is adjusted and clamped. (See fig. 9.) More sand is then thrown in between the bars and tucked under them with the hands and well packed upon the pattern. Still more sand is again added and well packed with the rammer, and this process is repeated until the proper depth is attained. The pieces for form- ing the holes are now taken out, the clamps are removed, and the cope is lifted off to one side, or, if furnished with hinges, may be turned back upon them in the manner of a trunk cover (fig. 10). The pattern is then carefully lifted out of its bed, and if any cor- ners or edges have been knocked off, or any other injury has been done, it is repaired with a trowel or some suitable tool. Pulverized FIG. 9. FIG. 10. Drag and Cope, opened. plumbago or charcoal is then dusted over the surface ; and if fine work is required, the pat- tern is replaced and carefully pressed down to give as much perfection to the impression as possible. This operation is technically called printing. The pattern is then gently tapped with the handle of a tool, to loosen it, and gently raised with the fingers or some appro- priate instrument, or by means of a screw in- serted into a hole previously prepared. Chan- nels are now cut in the surface leading from the points upon which the pieces for forming pouring holes stood to some part of the mould. The pieces still remaining in the cope are now removed and the holes are dressed. All par- ticles of loose sand are then blown from the