Gas Blowpipe for Brazing.
—Brazing blowpipes should be fitted with a combination air and gas regulator, by means of which both the size and nature of the flame can be adjusted to suit the work in hand. When choosing a blowpipe it is always better to make one rather larger than the work in hand necessitates—the flame can be reduced when required; by this means a margin of reserve is provided which is useful in emergencies. A blowpipe whose dimensions are 10 in. long, having a 5⁄8-in. gas supply reduced to 7⁄16 in. at the nozzle, and a 3⁄8-in. air supply reduced to 3⁄16 in. at the nozzle, will braze ordinary latch keys and other similar work if used with a No. 3 size blower. As already stated, a paraffin, petrol or benzoline blowlamp is a cheap and effective apparatus, especially where the quantity of work to be done does not warrant the outlay of a foot blower, gas blowpipe, etc., but gas has advantages over the liquid fuel, inasmuch as the blowpipe is more under control. The quantities of gas and air can be readily and more delicately adjusted during the actual brazing process, then as soon as the spelter fuses and the gas is turned off, the stream of cold air soon counteracts any excessive heat.