Making Tin Can Toys

by Edward Thatcher 1919


SOLDERING FLUX

Soldering Fluxes

Vice

Before tinning the point of the copper, some flux must be obtained, either a soldering paste or soldering fluid" killed acid." An excellent soldering paste called Nokorode is by far the best flux obtainable. It is inexpensive, a little goes a long way, and it will not rust or corrode the work as is the case with killed acid and some soldering pastes. It may be easily cleaned from the work after soldering and it makes soldering much easier and simpler for the beginner. Nokorode soldering paste may be obtained at any good electrical supply house or hardware store. If they do' not stock it, they wilt get it for you. There is nothing else just as good on the market, but if for an reason you cannot obtain this particular brand, be sure that any soldering paste you buy is plainly labeled that it will not corrode the work.

Soldering fluid or killed acid is made of muriatic acid in which is dissolved all the pure zinc that it will hold in solution. This fluid is much used by tinners and is certainly an excellent soldering flux, but not nearly as good as the soldering paste for our purposes. However, it is very useful in the shop to dip the tinned point of the hot copper into it to remove the oxide or dirt formed after the copper has been in use for some time. The solder will stick to the point much better after the copper has been cleaned in this manner.

Tinning Copper

Having procured the soldering copper and handle, some flux and soft solder, and having fixed up some sort of heating apparatus, the next step toward soldering is to coat the point of the copper with solder: this is called tinning the copper. Fix the copper firmly in a vise if one is at hand, as illustrated in Fig. 17. Then file each of the four faces of the point of the copper bright and clean with a flat file. It is better to use an old file for this purpose-one with rather coarse teeth. It will be observed that the copper is placed slantwise in the vise so as to bring one face of the square pyramid parallel with the vise jaws; this position permits filing in a natural horizontal position. Each face of the point should be rounded slightly toward the point.

If a vise is not available, the copper may be held, against the edge of the bench with one hand and the point filed clean and bright with the file held in the other, or a coarse sheet of emery cloth may be placed flat on the table and each face of the point rubbed bright on it. A file is by far the best for this purpose, however, and if it is chalked before using, the copper filed away will not clog it. When the copper is clean and bright at the point, each face should be thoroughly covered with a thin film of soldering paste or dipped into the soldering acid. The copper should then be placed in the fire and heated to the melting point of the solder.

Heating

While the copper is heating get ready a piece of tin about 2 by 4 inches-any clean flat scrap or part of a can will do. Spread a little soldering paste into the center of the tin and lay it on the bench near the heating apparatus. A few drops of killed acid may be placed on the tin instead of the paste, if the acid is to be used. After a few minutes heating the copper should e removed from the fire and the end of a strip of older touched to the point. If the solder melts quickly and easily against the point the copper is ready to tin; if it melts very slowly, "slushy" the copper should be returned to the fire and heated a bit more. The copper should never be heated hot under any circumstances; this must be borne in mind. If the copper is heated to a red heat, the soldering paste will be burned off and its action destroyed, for a red hot copper will not pick up solder, nor may it be tinned again until the copper is cool and refilled bright and clean, recoated with flux and reheated. If the copper is heated red hot after the point is tinned, the tinning is burned from the point and solder will not stick to it until it has been cooled, refilled and retinned.

This is the most important point to remember about soldering and is the cause of many failures. Remember that soldering is impossible without a flux to keep the metal clean when it is hot; too much heat will burn soldering paste or killed acid away; the tinning and the solder adhering to the point will be burned or oxidized and rendered brittle and useless. A heat that will melt the solder almost instantly and cause it to flow with a brilliant glistening color should be maintained at all times when the copper is employed for soldering. This is never a red heat. When the copper is first heated to be tinned, it should be removed from the fire when it melts the solder easily, and several large drops of solder should then be melted from the bar or strip or solder onto the piece of tin placed by the fire and on which some soldering paste or acid has been spread. Rub each face of the point of the copper into the solder on the tin until each face is thoroughly covered with a bright coating of solder. Hold each face flatly down against the solder on the tin during the rubbing process. The copper may have to be heated once or twice by the beginner, as it may get too cool to melt the solder easily. As soon as the solder begins to work stiffly, "slushy," and looks gray instead of glistening, it is time to reheat the copper.

An old piece of soft cotton cloth, such as a stocking, on which is sprinkled a little powdered sal-ammoniac is an excellent thing to keep handy when soldering or tinning. The tin coating of the point of the copper should be rubbed on this cloth where the sal-ammoniac is sprinkled, when the copper is hot. This will be found to keep the copper in excellent condition. The sal-ammoniac removes the oxide from the tinning and brightens it up generally about the point. The tinning will last much longer on the copper if it is dipped occasionally into the soldering paste or acid while hot. This is particularly true if the copper has been a bit overheated.

When the tinning shows signs of wearing off and the copper does not pick up solder readily, it must be retinned, filed, fluxed, heated, and rubbed on the solder which has been put on the tin first used for this purpose. This piece of tin should be kept about the bench, as the copper will have to be retinned frequently. Always remember that the copper will not carry solder to the work unless it is well tinned. If an electrical soldering copper is used it is usually furnished already tinned at the point, so that it is ready for use as soon as it is connected to a suitable electric socket and the current turned on. The heating coil inside the copper will soon heat it up to the melting point of the solder. After heating, it may be treated as a common copper, wiped occasionally on the cotton cloth and retinned when the tinning is worn away. An electrical copper should never be placed in a vise for filing, but should be held against the bench and filed carefully. A vise is apt to crush the hollow copper and injure the heating coil inside. These coppers should never be placed in a fire or heated in any way except by the electric current. Electrical coppers do not need as much attention as an ordinary copper for the even heat supplied by the current keeps the copper heated to the flowing point of the solder and is incapable of heating beyond this temperature.




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