Now, for practice, take two pieces of ¼-inch lead tubing and prepare them as for a cup joint, by spreading one end with the bending iron and rasping the other end to fit the cup, as shown in a, Fig. 33. Support them as you best can in an upright position. Flux the joint with rosin. Then take the solder in the left hand, set the lighted candle at the right hight and distance from the joint, as shown at B, Fig. 47, which leaves the right hand free to manage the blow pipe. Then heat the joint with the flame, and, as it gets hot, touch the joint with the solder, and when it reaches the melting temperature of the solder a drop of it will detach itself and flow clear around the joint, making a smooth, clean joint that is stronger than the pipe itself.
Joints made in this manner present a handsome and workmanlike appearance to the mechanical eye. Practice diligently on the lead pipe until you have become so proficient that you can flow the solder all through the joint without withdrawing the flame. Then procure some ⅜-inch block tin pipe, and, when that can be soldered perfectly, the beginner can consider himself sufficiently proficient to practice on flat seams on Britannia metal.
Soldering Britannia Metal.
For working Britannia metal the candle cannot be used, as the dripping grease will cover the work and seriously interfere with the flowing solder. The beginner must provide himself with an alcohol or kerosene torch. A good form of torch, manufactured and sold for electricians' use, is shown in Fig. 48. The alcohol gives a clean flame, but by comparison is somewhat expensive. The kerosene gives a flame that can be concentrated on a small surface with fully as much heat, and if care is taken to allow only the blue flame to touch the work, it is fully as clean and cheaper.
Fig. 48.—Alcohol or Kerosene Torch.
Fig. 49.—A Specially Constructed Torch.
The burning kerosene torch gives off a dirty smell and smoke, which makes it disagreeable to handle, but this is a case of take your choice, and it is left to the beginner to use either, as they will both do the work satisfactorily. It is also necessary, in doing this work, to have the blow pipe attached to the torch and connected to the mouth with a piece of very small rubber tube. This will leave one hand free to apply the flux and hold the solder. The flame can also be quickly placed in any position or directed to any portion of the work without allowing the work to cool. The alcohol torch for this work should be so constructed that it can be held in a horizontal or inverted position without spilling the contents of the torch.
The handiest, as also the cheapest, torch to make is the one shown in Fig. 49. It consists of a can 3 inches high made in the shape of a frustum of a scalene cone. The tube B should be ¼ inch in diameter, and must run parallel with the flaring side and extend half way to the bottom of the can, as e. Then, when the torch is tipped to solder horizontal work, the alcohol will flow into the space a, leaving the alcohol to supply the wick to be drawn up by capillary attraction. This tube is made of ¼-inch brass tubing, bent to form an angle with the can, as shown.