Edward Thatcher

PREPARING A JOINT FOR SOLDERING—CLEANING AND SCRAPING—SOLDERING A PRACTICE PIECE—SOLDERING THE HANDLE TO THE BISCUIT CUTTER—A SECOND PRACTICE PIECE—ANOTHER METHOD OF APPLYING SOLDER

Cleaning and Scraping.—If the copper is thoroughly tinned and the heater and materials are ready for use as described in Chapter IV, then several practice pieces should be soldered together before attempting a joining on any real work you may have ready to solder.

If the tin is bright and clean, it need not be scraped at the joint where the solder is to go. Rusty spots should be scraped bright if in the path of the solder. Paper, labels or paint must be cleaned away. If a can has been well rinsed with hot water when the contents are emptied, it will present no difficulties to the soldering, but a can that has been emptied but not rinsed presents a more difficult surface to solder; particularly tomato, fruit, or condensed milk cans. This, of course, applies only to the inside of these cans. Tobacco, coffee, cocoa, tea cans and the like offer no resistance to the solder without washing. The yellow lacquer used to line some cans need not be scraped off. Solder will adhere well to tin so treated, but paper, paint, etc., must be scraped from the path of the solder. The scraped part need only be a quarter of an inch in width on each side of the joint; the rest of the paper labels or paint will be removed in the hot lye bath used before painting the can.

The scraping may be done with an old knife, or a regular scraper furnished by the dealer in tinners’ tools as illustrated on page 202, Chapter XXI.

When scraping the tin bright, do not scrape it so hard that all the tin will be scraped away from the inner sheet of iron, as solder will stick to tin much better than to iron. If the tin is not very dirty, a piece of emery cloth or sand paper may be used to clean the joint.

Paint cans, cans that have contained stove blacking, rubber cement, varnish, shellac, etc., should be thoroughly boiled in a strong lye bath before soldering; paint is usually made of oxides and oxides are a sure preventive of soldering. The lye bath is made by adding two heaping tablespoonfuls of lye or washing soda to the gallon of boiling water. Cans boiled in this solution for five minutes will be thoroughly cleaned and free from paint, paper labels, and practically anything likely to be found inside or outside of a can. The lye or washing soda may be obtained at any grocery store. Care should be taken not to get any of the lye solution on the hands or the clothes as it is very caustic and will burn the hands and ruin the clothes if not immediately washed off. The work should be handled with a wire hook while in the bath and well rinsed with water when removed from it. The same lye bath is used before paint is applied to tin work, when all forming, soldering, riveting, etc., is done. It removes the flux, acid, and finger marks, leaving a clean surface on which to paint.

Soldering a Practice Piece.—For practice in soldering, an angle joint is a good thing to begin with; something that is small and easily held in position while being soldered. As I have already described the forming up of a biscuit cutter to the point of soldering it together, a practice piece resembling it will be an excellent thing with which to begin.

Cut a narrow strip of tin about 1 inch wide and 4 inches long and a flat piece of tin about 2 by 3 inches. Be sure that the ends of the narrow strip are cut squarely across, using the square if necessary. (See chapter on “Laying Out Work,” page 32.) See to it that both pieces are well flattened out and smooth.

Bend the narrow strip into a semi-circular form, like the biscuit cutter you have already to solder and stand this piece in position on the larger flat piece of tin.

Now lay the piece near the soldering copper heater, on the wooden bench; be sure to place it on wood, not on a part of the vise or any other metal that may be convenient. Iron, stone or brick will absorb too much heat from the tin if directly under and in contact with it, and thus prevent soldering.

Apply a small amount of soldering paste to each joint as indicated in Fig. 18. The paste may be applied with a small flat stick of wood such as a match stick shaved down to a long, thin, wedge point.

Killed acid or soldering fluid is usually applied with a small camel’s-hair brush set in a quill; sometimes a chicken feather is used for this purpose.

The flux, whether paste or acid, should be applied sparingly, but be sure that enough is applied to thoroughly cover the joint, as if it were painted on both sides of the metal where it joins.

See to it that the copper is well tinned and heated until it will melt and take up a good sized drop of solder at the point when held against a bar or strip of solder. Wire or strip solder is much easier for the beginner to handle than the heavier bar. It melts far more easily, as it is smaller.

If bar solder is used, place it on an anvil or stone and hammer one end out, until it is about ? inch thick and much wider than the original bar. It will melt off much more quickly when thinned out.

Hold the semi-circular piece in position with the left hand and with the right bring the hot copper charged with molten solder at the tinned point and fit the point of the copper closely into the angle formed by the joint, moving the copper very slowly along the joint, starting at one side and finishing at the other.

When each side of the joint is thoroughly heated up to the melting point of the solder, some of the solder will leave the copper and flow into and over the joint; so that when starting to solder a joint the copper should be allowed to rest a moment where the soldering is to be started. The tin is then heated up and when the solder starts to flow into the joint, the copper is drawn slowly along, heating up the tin, and as it travels flowing the solder into the joint.

The following points should be well remembered when soldering:

That the tin, to be soldered, must be heated up to the melting point of the solder before the solder will leave the copper and adhere to the tin.

That the copper supplies the heat to the tin and that the tin will not be heated unless the copper is kept in contact with it long enough to heat it. Enough of the copper should be in contact with the tin to be soldered for the heat to flow quickly into the tin, see Fig. 18. Do not merely touch the point of the copper to the joint and expect it to heat that joint: it won’t. Two faces of the point of the copper should rest against the parts of the work to be soldered, thus transmitting heat to the pieces as shown in Fig. 19. If too much of the point is allowed to come in contact with the work, the solder will be smeared over the work in a broad unnecessary stream. This is the reason that the points of coppers are filed slightly rounding toward the point.

Remember: That the copper must be hot enough to make the solder glisten.

That a red-hot copper will not pick up solder.

That a red-hot copper burns away the flux, and that it destroys the tinning at the point of the copper; a red head also oxidizes the solder, making it brittle and weak.

That solder will not fill up a gap in a joint unless in very expert hands; joints should fit closely.

That a good joint should appear smooth; look as if painted on. A smooth joint is produced by a hot copper, clean metal, and good flux, but most of all, by leaving the copper long enough in the joint to heat it thoroughly.

That small joints are heated and soldered almost instantly.

That large joints require a longer time to heat up and that very heavy work requires a large copper and sometimes an outside source of heat as well—but we have nothing to do with such work in this book.

That work must be held together until the solder sets or turns gray, as it may spring apart while the solder is molten.

These are all very simple facts and should not be difficult to remember.

To continue with the practice piece: As soon as the solder has run in and around one end of the practice joint, remove the copper and solder the joint at the other end of the piece. As these joints are small, they should heat up and solder very quickly. One heating of the copper should do for both joints, but be sure that the copper is hot enough before you try the second joint.

If difficulty is experienced in making your first joint and it does not stick together, apply more flux and try again.

The handle may be soldered to the biscuit cutter in the same manner after the practice piece is successfully completed.

Another Method of Applying Solder.—Sometimes bits of solder may be cut from the strip of wire solder and placed in the joint to be soldered. The hot soldering copper is then used to melt the solder into the joint. The joint must be well fluxed before the solder is placed in position.

The end of a strip of wire solder is sometimes held against the point of a hot copper as it is moved along a joint to be soldered. The solder is fed against the point of the hot copper as it melts into the joint.

Both of the above methods will be found advantageous when a gaping joint is to be filled with solder and it is desirable to apply a quantity of solder in one place.