Manufacture of Cannon

—Cannon for the U. S. service are made by private founders. The material and product of the casting are under the supervision of an ordnance officer, who receives the pieces only after they have satisfied all the conditions imposed by the regulations of the service. There are several foundries for making cast-iron cannon. Wrought-iron field cannon are principally made at the Phœnixville Iron-Works, Pa. There are also several private establishments where special cannon are made. The several operations of manufacturing cannon are, molding, casting, cooling, and finishing. Molding , in general terms, is the proce by which the cavity of the form of the gun is obtained by imbedding a wooden model in sand, and then withdrawing it. The wooden model is technically called the pattern, and the sand is confined in a box, which is divided into two or more parts for convenience in withdrawing the pattern. The pattern of the piece to be cast, somewhat enlarged in its different dimensions, is composed of several pieces of hard wood, well seasoned, or, for greater durability, of cast iron. The first piece of the model comprises the body of the piece from the base-ring to the chase-ring; the swell of the muzzle, and the sprue, or dead-head, are formed of the second piece; the breech, of the third; and the trunnions, of the fourth and fifth pieces. The sprue, usually called the “head,” is an additional length given to the piece, for the purpose of receiving the scoria of the melted metal as it rises to the surface, and furnishing the extra metal needed to feed the shrinkage. Its weight also increases the density of the lower portion of the piece. The breech is slightly lengthened in the direction of the knob of the cascabel, to form a square projection by which the piece can be held when being turned and bored. The best material for the mold is dry, hard, angular, and refractory sand, which must be moistened with water in which strong clay has been stirred, to make it sufficiently adhesive; when not sufficiently refractory, the sand is vitrified by the high temperature of the melted metal, and protuberances—not easily removed—are formed on the casting. When not sufficiently coarse and angular, the materials cannot be so united as to preserve the form of the molds. The mold is formed in a case of cast iron, and termed the “box,” or the “flask,” consisting of several pieces, each of which has flanges perforated with holes for screw-bolts and nuts, to unite the parts firmly. To form the mold, the pattern for the sprue and muzzle, previously coated with pulverized charcoal or coke, moistened with clay-water to prevent adhesion, is placed vertically on the ground, muzzle part up, and carefully surrounded by the corresponding parts of the jacket. When properly adjusted, the sand, prepared as above, is rammed around it. The model for the body of the piece is then placed on the top of this, and the corresponding parts of the jacket correctly secured, and filled in succe ion with the molding composition. The patterns for the trunnions and rimbases are bolted to the model of the piece, and when the sand is rammed firmly around these, the bolts are withdrawn, this part of the mold completed, and the end-plates screwed on. After completing the mold for the body of the piece, the model for the cascabel is properly adjusted and the mold completed. Care is taken to cover each portion of the model with the coke-wash mentioned above, and to sprinkle dry sand upon the top of the mold in each piece of the jacket, to prevent adhesion, so that the portions of the mold may be separated. In the body of the sand, a channel for the introduction of the metal is formed in the same manner as the mold cavity. It enters at the bottom of the mold, to prevent the bottom from being injured by the falling metal, and in an oblique direction, to give a circular motion to the metal as it rises in the mold, and thereby prevent the scoria from adhering to the sides. When the mold is completed, the parts of the flask are carefully taken apart, and the pieces of the model withdrawn from the mold contained in them. If any portions of the mold be injured in withdrawing the model, they are repaired, and the interior of the mold is covered with coke-wash; after which the several parts are placed in an oven to be gradually and perfectly dried. When this is accomplished, the parts are carried to a pit, where they are united and secured in a vertical position, with the breech below. Any portion of the sand broken off during the movements and adjustments should be replaced, and the whole of the interior covered with coke-wash. The object of coke-wash is to prevent the sand from adhering to the melted metal, which, when prepared, is made to flow in at the entrance of the side-channel. As the metal rises in the mold, a workman agitates it with a long pine stick, to cause the scoria and other impurities to rise to the surface, and brings them toward the centre of the mold, to prevent their entering the cavities for the trunnions.