Welding; theory, practice, apparatus and tests, electric, thermit and hot-flame processes . it were the negative pole,more heat would be lost and the carbon from the pencil wouldenter the weld and harden the metal. While if an alternatingcurrent were used, some of the carbon would enter the hot metal, THE BERNARDOS ARC-WELDING PROCESS 39 while the weld would not receive more than half the heat ofthe arc. Table, Switches, Controlling Apparatus, Carbon.—The tablewhich holds the work is of cast or wrought iron. The metalto be welded is laid on the table, and it is supposed that thecontact between
Welding; theory, practice, apparatus and tests, electric, thermit and hot-flame processes . it were the negative pole,more heat would be lost and the carbon from the pencil wouldenter the weld and harden the metal. While if an alternatingcurrent were used, some of the carbon would enter the hot metal, THE BERNARDOS ARC-WELDING PROCESS 39 while the weld would not receive more than half the heat ofthe arc. Table, Switches, Controlling Apparatus, Carbon.—The tablewhich holds the work is of cast or wrought iron. The metalto be welded is laid on the table, and it is supposed that thecontact between table and metal will be sufficient to carry thecurrent. If the piece of metal is small, the positive lead had bet-ter be clamped directly onto the metal instead of the table. The switchboard contains a single-throw switch and arheostat connected with grids. Or the rheostat may be made ofwater-barrels with insulated sides and a terminal plate for abottom. The other terminal is also a metal plate suspended overthe barrel. It is lowered in and out of the water of the barrel. ShieldLead. Fig. 14.—Carbon negative pole and shield. The trouble with barrel rheostats is that the water is liable to boilover under continuous usage, while the barrel hoops will rust rap-idly. Circuit breakers should be used to prevent the armaturefrom burning out, in case the operator accidentally short-circuitsby touching his carbon pencil to his work. The carbon pencils are made in sizes of 1/4-inch to i 1/2-inch diameter by 6 to 12 inches long—of sound carbon. Thecarbon pencil is fixed into an insulated handle. Midway on thehandle is a round shield to protect the operator from the flameof the arc and from sparks (see Fig. 14). Workmans Protective Apparatus.—Under this head comerubber gloves, a leather or rubber suit or apron, a hood of cloth,stovepipe or wood for the head, and a pair of glasses for the in mind that the operator is manipulating a current of highvoltage and also an arc o
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Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1910
