Fig. 3001.
In the following figures (which are taken from Mechanics) is illustrated the method employed to build up the shaft shown in [Fig. 3001], which was for the steamer Pilgrim. Forgings of such large dimensions are built up of pieces or slabs, called blooms, which are themselves forged from scrap iron, which is piled as in [Fig. 3000]. For the forging in question this scrap iron consisted of old horseshoes, boiler-plate clippings, boiler rivets and old bolts, and the first step in the manufacture is to form this scrap into piles ready for the furnace.
Fig. 3002.
Fig. 3003.
These piles are made upon pieces of pine board 1⁄2 inch thick by 16 inches long by 10 inches wide. On these the scrap is piled about 14 inches high, each pile weighing about 270 pounds. After piling, the scrap goes into the furnace and is raised to a welding heat, the board retaining its form as a glowing coal almost to the last. The pile of scrap is heated so nearly to melting as to stick together enough so that it can be picked up in a long pair of tongs with peculiarly-shaped jaws, and, as these tongs are suspended by a chain from an overhead traveller running on an iron track, the bloom is easily transferred to the anvil of the steam hammer, where, after one or two blows, a small porter-bar with a crank end, such as shown in [Fig. 3003], is welded on, and the pile is rapidly drawn out into a square bar. When completed the porter-bar is cut off, and the bar is laid aside to cool. The pile of scrap has now become a “bloom,” such as shown in [Fig. 3002], and has been reduced in weight from 270 lbs. to 240 lbs. The bloom is about 30 inches by 5 inches by 5 inches in dimensions, and has rounded, ragged ends, and a surface full of lines marking welding of the individual pieces, and at the ends looking as though the scrap had united by melting rather than by any welding process.