The blowpipe shown in the accompanying illustration will be found a very useful adjunct to any mechanic's workshop. For tempering tools, heating soldering irons, brazing, and melting metals in a crucible, it answers the purpose of the more expensive outfits, which the amateur as a rule does not feel able to invest in. Furthermore, there are no bulky air tanks and pumps to take up room, which to most amateurs means a great deal. The one illustrated can easily be carried in the pocket, so it is evident that the space required is indeed small. To construct one of this size, about 6 feet of copper or brass tubing 5/16 of an inch outside diameter will be required, also 2 feet of band iron about 1/16 of an inch thick by 3/4 of an inch wide. Before bending the tubing to the required shape, it is necessary to fill it with lead or sand to prevent buckling. Either of these will be found to give good results, though for the smaller sizes of tubing lead is preferable. It is not advisable to attempt pouring the molten lead in the tube, as it cools too rapidly. The safest way is to use wire solder. A piece two or three feet longer than the tube will as a rule be enough. The lower end of the tube will have to be closed by hammering it down. Insert the wire solder, hold the lower end of the tube over a flame to melt the solder, at the same time pressing the wire slightly. Move the tube slowly over the fire and it will quickly melt the lead, and one may feel sure there are no bubbles. To form the coil, use a round bar about 7/8 of an inch in diameter. A broom handle will prove useful. It is best to reduce the nozzle a slightly, to increase pressure of the gas as it becomes heated in the coil. After this is clone, and the coil assumes the shape shown, we can proceed to remove the lead, which may be easily done by heating over a fire until the lead melts, then by shaking slightly it will run out and leave the tube clear. The valve may be dispensed with, and a rubber tube from a convenient gas jet may be slipped on.

Fig. 136 - Details of the blowpipe.

Fig. 137 - The blowpipe in use.

This blowpipe is adapted for gas under considerable pressure. If the pressure obtainable is low a larger pipe should be used and be bent into a smaller coil, and the constriction at a will be unnecessary.