. Dental metallurgy, for the use of dental students and practitioners. 84 METALLURGICAL APPARATUS to melting operations involving quantities exceeding oneounce. In such cases it is better to employ a crucible andany stove or furnace in which the temperature can be raisedsufficiently. This may be accomplished in an ordinary cook-ing stove, a blacksmiths forge, or a small fire-clay furnace,by the use of anthracite coal, coke, or charcoal. Fletcher Furnace.—By far the most convenient, compact,and effective furnace for melting from 1 to 10 ounces ofgold, which has ever been used, is the crucible f
. Dental metallurgy, for the use of dental students and practitioners. 84 METALLURGICAL APPARATUS to melting operations involving quantities exceeding oneounce. In such cases it is better to employ a crucible andany stove or furnace in which the temperature can be raisedsufficiently. This may be accomplished in an ordinary cook-ing stove, a blacksmiths forge, or a small fire-clay furnace,by the use of anthracite coal, coke, or charcoal. Fletcher Furnace.—By far the most convenient, compact,and effective furnace for melting from 1 to 10 ounces ofgold, which has ever been used, is the crucible furnace (), invented by Mr. Fletcher, which can be obtained at thedental depots. The furnace is perfectly adapted to the wantsof the mechanical dentist. It is composed of a substance. Fig. 26 resembling fire-clay, but much lighter in weight, and said topossess only one-tenth its conducting power for heat. The furnace consists of a simple pot for holding thecrucible, with a lid and a blow-pipe, all mounted on a suitablecast-iron base. As compared with the ordinary gas furnaceit appears almost a toy, owing to its great simplicity. Thecasing holds the heat so perfectly that the most refractorysubstances can be fused with ease, using a common foot-blower. Half a pound of cast-iron requires from seven totwelve minutes for perfect fusion, the time depending on thegas supply and the pressure of air from the blower. Thepower which can be obtained is far beyond that requiredfor most purposes, and is limited only by the fusibility of the HEATING DEVICES 85 crucible and casing. The crucible will hold about ten ouncesof gold. An ordinary gas supply-pipe of ^ or | inch diam-eter will work it efficiently. It requires a much smaller supplyof gas than any other furnace known; abou
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphila, bookyear1917
