FOUNDRY PRACTICE. Cart The casting of brass has been practise: the earliest times and is mentioned in hooks of the Bible. Before the yot wrought iron was made directly fry This nearly pure iron cannot by methods be made sufficiently fluid to molds. By special methods in recent is made into steel castings (q.v.). At casting temperatures it is pasty and .7. forged into various shapes. Until la a, were generally made directly from tkti furnace in which cast iron was made ore. The first casting known to have tetc in America was a small round-bottock with a cover, made at Lynn, Mass. in the first blast furnace erected in this a: In 1722 a French founder made the firs five cupola. Foundry practice dates irr time. The ordinary cupola was an upri, furnace thickly lined with firebrkk r were placed alternate layers of pig fuel. A tap-hole at the bottom served off the molten metal. to fill the molds i-t• ing. Before the beginning of the last cr. rarely more than a single casting from one pattern. Each new form new pattern as well as mold.
The only foundry equipment until years was the cupola, a blower, a ladles, cleaning mills, sweeps for loam the molder's individual tools: a shovel. rammer and trowels, some of which ' slicks. By the duplication of patterns in later years molders have Y' expert in special classes of work Mt' when working by the piece. When larg:' bers of a single kind of castings are to be': a molding machine can be employed ously and these are rapidly coining Machines can be operated with congz" unskilled labor. Modern foundries are with electricity and compressed air, trif cranes and trolleys, which are used tc'' port materials, and to do the heavier the molder's work. While permaneet molds are used for the softer metal have not been made successful for brass sn. The improvements in machine forging led to the discarding of many parts of ines formerly cast, but now made much durable in wrought iron or steel. See NINE FORGING.
and of various grades is used almost uni illy for molds, and the founder's art con in the making of sand molds. Molding is a mixture of silica sand and clay with 10 to 15 per cent of impurities. It is ig if when dampened and pressed into e it will not fall apart. Fine sand gives castings a smooth skin. Heavy castings ire a coarse open sand. The reddish color olding sand comes from iron oxide. After castings are removed from the sand it is Bled into a row, then, with the shovel, ed up and sprinkled evenly with water. next morning beginning at one end the is cut over, giving each shovelful a twist caner the sand evenly over a new heap.
ut once a week enough new sand is added lake up for what is burned out.
VIolding.— The different branches of mold have much in common. We will describe simplest form and then show where the .r forms differ.
Bench Molding.— The patterns for toys, l•are, small parts of stoves, light malleable t and many brass castings are made of al, gated together so that the card of pat is is handled as a single piece. Melted iron °tired into a vertical sprue and runs to the d through horizontal passages called gates. card of patterns is bedded in a mold-board ed a match which closely conforms to every ing or horizontal edge of the pattern.
The molder works standing, his match of :erns being placed on a frame or bench, h his heap of sand beneath and at the side.
mold is made in a snap flask, the lower t of which is the drag and the upper part the e. These arc guided together by flask-pins both are hinged at the corner and hooked ether at the opposite corners. The pattern horoughly brushed when the drag is inverted the match. About half an inch of sand is died over the surface of the pattern. The kg is then heaped up with sand with a shovel. ken with a hand rammer, about 13 inches ig, in each hand, the molder penes the edges the drag twice around with the flat pene of rammers, and levels off the surface with side of the rammers. With the round butt ds the whole surface is rammed solid. The rplus sand is struck off with a straight edge, ittle sand is sprinkled over the surface and a nom board is rubbed to a fit. This with the ag and match are rolled over and the match lifted off leaving the pattern bedded in the nd, when all loose sand is blown off with a llows, and necessary repairs are made with a ck. The cope is put on, the sprue pattern is t on a pin in the gate pattern and a little .rting sand is dusted over the surface. This irned parting sand, cleaned from castings, the cope from sticking to the drag. The cope is rammed the same as the drag, Le loose sand brushed off, the sprue removed id the hole smoothed with the fingers. The lie is lifted and placed on edge just behind le drag. The pattern is drawn and is held in the left hand while a bag of charcoal facing is shaken over the mold with the other. The pat tern is printed back, rapped and drawn. The cope is then replaced on the drag, the flask is unhooked and the sand mold with its bottom board is set on the floor.