=Making a Gas Brazing Hearth.=--The brazing hearth can be bought ready-made, or can be cheaply put together by the worker himself, the necessary materials consisting of two bellows, some lead piping, and an old packing case to support a large size frying-pan--about 1 ft. 4 in. by 1 ft. The bellows are fixed one above the other, interconnected by a fixed lead pipe, one pair of bellows worked by the foot pumping air into the pair above it, from which the air is taken to a bunsen blast burner by flexible tube. This bunsen burner can also be easily and cheaply made, and as this works very well and will be found useful for both soldering and brazing, the following hints on making it are given. First, get two ordinary large house bellows about 1 ft. square, or larger if possible; the larger the better. Next a good strong packing case about 2 ft. long by 1 ft. 3 in. high and 10 in. wide is required. One end of the box will form the base, and to make it steadier two 1-in. boards should be screwed across to protrude about 6 in. on each side, the front one being considerably wider, as can be seen at T (Fig. 62), which shows the apparatus with one of the case sides removed. The packing case proper is denoted by the letter A; the part A S A was formerly the bottom of the case, but is now the back; and the top A V A was the end of the packing case. Half-way between the top and bottom a shelf B should be fixed, having a large hole cut out of the middle at G to accommodate the union piece (seen in section), which holds the lead air-pipe communicating from the lower bellows to the upper.
[Illustration: Fig. 62.--Home-made Brazing Hearth]
In the back, near the bottom, at S, cut a hole for the nozzle of one of the bellows, and above the shelf cut another hole at S^{ 1} to take the nozzle of the other bellows. The bottom bellows C should have the top handle extended by a piece of stout bent iron N to act as a pedal, and should be screwed to the base. A central hole about 3 in. in diameter should be cut at P to allow the air to reach the valve. Now get a piece of lead pipe 1/2 in. inside diameter, and, having cut down the nozzle to just under that diameter, force the mouth of the pipe over it as at S, and bend the pipe F as shown, to reach the centre of the shelf B and enter the hole G until flush with the top. Remove the lead pipe and get a block of wood about 3 in. square. Cut off the corners and bore a hole in the middle, so that the lead pipe will just pass through it, and countersink the hole. Broach out the mouth of the lead pipe until it becomes bell-shaped and fits the block of wood, so that its edge is flush with the wood when pressed hard against it. This is clearly shown at G, where the dark shading represents the wood block. Cut a leather washer the size of the block, with a 1/2-in. central hole, and lay this over the hole in the bottom of the top bellows where the leather flap valve is. Bore two holes in the wood block, and screw this down tightly to the bottom of the bellows, so that the bell-mouth of the lead pipe faces the hole and has the leather between it and the block. This should make an air-tight joint for the fixing of the pipe to the bellows.