Simple soldering

In looking through many books on the subject of soldering and in an almost daily use of the processes described in the following pages, it has seemed that something more might be written of, "how" rather than "why."

The action of metals under heat; the unions resulting from the melting and amalgamations or welding properties of certain metallic combinations; the fluxes required to clean and protect the metals to be joined; the number of degrees of heat needed, etc.; are aptly described in other works.

But the method of securing the desired result in the simplest possible manner is not often clear, and to that end this little book is written.

The Uniting of Metals, by a fused metallic substance, or metallic cement as the dictionary has it, is what is known as soldering.

In order that the metals be properly united with the metallic solder they must be perfectly clean and free from dirt or oils of any sort, and so are usually scraped with a knife-like instrument or rubbed bright with emery cloth. To further clean the metal and render it clear of all dirt and oxide from the source of heat a "flux" is used.

The class of work requiring soft solder, and the class of work to be hard soldered are usually of quite different types.

Soft Soldering. The metal used for soft soldering is usually a mixture of equal parts of tin and lead. This has the advantage of requiring a much lower temperature to fuse it than the metals which it is to unite.

The Flux used for soft soldering is usually resin or "killed acid," the latter being known as soldering fluid. The purpose of this flux is simply to keep the metals clean where soldered or rather, where they are to be united by the solder.

Hard Soldering or Brazing. Silver or brass is used as the uniting metal (brass solder is known as spelter). This of course makes a much stronger joint than soft-solder; but the higher degree of heat needed to melt the silver or brass solder makes it often useless for jobs which will not stand a high degree of heat. Hard Soldering also requires more complicated apparatus to attain the required amount of heat.

The Flux used for Hard Soldering and Braz- ing is usually borax dry or in the form of a paste. Muriatic acid is also used for special kinds of work.

Both processes have come to be used for certain things well suited to the conditions of their several merits, and the matter on the following pages is intended to make this clear.


Soft Soldering

Soft Soldering is generally known as something that is accomplished with a soldering iron or copper, which is a piece of copper weighing from a few ounces to several pounds firmly attached to an iron rod having a handle. It is usually heated in a charcoal or gas furnace until it will melt soft solder and then removed and placed in contact with the joint to be soldered. Thus heating up the metals to be united as well as the solder on the spot where the solder should "run" or flow and adhere.

This method has its advantages, but I think many amateurs try to make joints by this method greatly to their detriment instead of resorting to direct heating with the flame which will be described first.

Heating the Work. No matter how the heat is conveyed to the joint it must be remembered that both pieces to be soldered must be heated equally or else the piece which receives the most heat, usually the smaller, will absorb all the solder. It is a safe rule to always heat the larger piece first, allowing the smaller pieces to receive their heat from the larger ones. Both metals to be joined must be heated to the melting point of the solder.

Flux for Soldering. Before we can make a perfect joint we must have a proper flux. For many purposes resin is used, but soldering fluid serves almost wholly for all small work except electrical connections. For electrical work a special soldering stick is made from resinous compounds. This may be purchased at any electrical supply house. Resin may be had of the hardware merchant. But the cleanliness of soldering fluid makes it advisable for general use. In electrical work some engineers maintain that the acid corrodes the metals, others say it does not; many use' it, but the soldering stick is generally used. When making experimental models in metals, attaching pins to jewelry and all such work use the soldering fluid which may be purchased readymade, or can be prepared in the following simple manner.

Soldering Fluid. Use an open mouth pint fruit-jar and pour in about half a pint of chemically pure muriatic acid. Then get some pure zinc. Battery zincs are best because pure. The zinc used under stoves, and about the shop is not pure. Use only the purest zinc there is to be bad.


Hard Soldering or Brazing

Some forms of hard and soft soldering are carried out by exactly the same manner of operation, the only difference being in the solder, the flux, and the degrees of heat required.

Hard Soldering requires a much greater temperature since silver or brass are generally used as solder and borax in some form as a flux. A much stronger flame is needed; that of a current of gas and air under pressure being preferred, or a gasoline or alcohol torch. In large heavy work the blacksmith's forge, a charcoal fire or a specially heavy blast of gas or gasoline is used. As in soft soldering the work must be thoroughly cleaned and scraped bright first.