Closely allied to welding is a method of uniting iron and steel called brazing. By this means two pieces are soldered together by a brass alloy. It is used where the parts are so small or thin that they would be burned or wasted away, if they were to be raised to a welding heat. Brazing is also used where finished parts that must not be stretched or upset by hammering are to be joined. The method is very simple. The parts to he joined are made bright and cleaned of all acid or grease. Paint the parts with some flux, such as borax, and raise to the melting point of the brass. Sprinkle brass filings over the joint. The parts, to be joined, must be firmly fastened while being heated. The brass should contain enough zinc so that its melting point is well below that of the iron. It should melt when the iron or steel has come to a bright cherry red. The brass must melt thoroughly or it will not adhere to the metal. Be very careful not to get the iron too hot. The heating had best be done on a charcoal or anthracite fire. Soft coal can only be used where the greatest care is exercised. The presence of sulphur in this fuel gives very poor reaulta.
A method that is much easier to handle is now in extensive use, A graphite crucible is used, in which a quantity of brass is melted. The parts to be brazed are brightened and fastened together in the usual manner. Then they are painted with a flux such as borax paste. The parts not to be joined are painted with an anti-flux. For this a special preparation of graphite made by the Dixon Crucible Co., will answer. When the brass has been melted and the parts prepared as directed, the latter are plunged into the molten metal and held there until they have risen to the temperature of the same. They are then taken out, wiped, and the superfluous metal filed away. This method is extensively used for brazing bicycle frames and in doing work of a similar character.