Soldering on the best work should be used very seldom, and all the fastenings should be either done by riveting, screwing, or brazing; and I need hardly remark that no part of a boiler should be soldered which comes in direct contact with the flame of the lamp or furnace.
Brazing, with the exception of very small articles, is beyond the ordinary powers of an amateur.
Even to braze the seams of a model boiler requires a forge fire or very powerful gas-blast, which is too expensive for most boys to get; but small things, such as a broken slide, valve rod, etc., can be easily brazed by using a gas blow-pipe, and as it will cost you very little to make and will prove a useful tool for sweating in solder as well as brazing, I will briefly explain.
Fig. 1.
[Fig. 1] is a section of the blow-pipe complete.
To make it, first get a small piece of brass tube (A) of about half an inch diameter and five inches long; drill a hole at two inches from one end, and insert a piece of gas tube (B) and solder it in place.
Next take a piece of glass tubing a quarter of an inch diameter and about seven inches long, hold one end in a gas flame, and when red-hot draw it out to a fine point, then file round and break off the tip, leaving a small hole.
Next squeeze a sound cork into the tube A as at C, and drill a quarter of an inch hole through its centre and insert the glass tube D, and the blow-pipe is finished. To use it you connect the pipe B with a gas bracket by a rubber tube, and the glass tube D must be fastened to a pair of bellows by means of another piece of rubber tubing; the bellows should have an air-bag attached, to enable you to keep a constant pressure up and prevent having a jerky flame.
When requiring to braze any article, bind the parts together with some very fine brass wire and cover it up with a little powdered borax and water, then lay the article on a piece of charcoal, and if it is necessary to preserve the temper of the steel you are about brazing, cut a potato in half and push each end of the steel rod into the halves, which will prevent the temperature of the rod getting too high.