SHEET METALS 457 



then to clean the parts to be soldered -thoroughly. A solder 

 with as high a melting point as possible should be used and 

 the heat applied so that the temperature of the work to be 

 joined is brought as near as possible to the fusing point of 

 the solder. Thus the solder will be allowed to flow freely and 

 a better union will result. 



542. Aluminum Solder. Aluminum solder consists of 

 aluminum, phosphor-tin, zinc, antimony, and an acid. In 

 forming the solder, the zinc, tin, and antimony should be 

 melted before the acid is added. The following flux should 

 be used in soldering aluminum: 12 oz. zinc chloride, 1 oz. 

 sal ammoniac, and 13 oz. water. 



Zinc chloride as a flux is made by adding zinc shavings or 

 pieces to muriatic acid until the bubbles have disappeared. 

 The zinc chloride formed in this way is often called cut-acid 

 or killed (neutralized) acid to distinguish it from the muriatic 

 acid, which is also used as a flux. 



An acid flux, like muriatic acid and zinc chloride, should 

 never be used on an electrical connection or on any article 

 that is to be painted. An alcoholic solution of rosin is a 

 good flux for this work. 



543. Brazing Metals. The flanges and fittings for copper 

 pipes are made of an alloy of 84% copper and 3% zinc, 

 called brazing metal. Brazing solder must contain more 

 zinc than tin in order to have the solder fuse before the copper. 



544. Shears for Cutting Metals. Since sheet metals 

 come into the trades in flat sheets, shears for cutting 

 these sheets have been devised. There are two kinds of 

 shears, namely, a power shear for cutting out edge lines, 



