In making connections with soft pipe it is better to make use of brass couplings, and these can be soldered more easily and safely by means of the blowpipe than with a bit. First clean and tin both ends of the coupling, and with the bit put a little ring of solder round about 1⁄8 in. from the end, as shown at D in [Fig. 42]. Next with a penknife cut a hole in the pipe B where the connection is wanted, a neat fit for the end of the coupling tail A, scraping the surface of the pipe all round the hole. Insert the coupling in the hole in a vertical position. Sprinkle a little powdered resin round the joint, or smear it with fluxite. Using the flame of a spirit lamp or a candle and a mouth blowpipe, heat the upper part of the coupling, being careful not to allow the flame to come too near the soft pipe. The solder will soon melt, and run down into the joint (see D in [Fig. 43]), when the flame must be instantly withdrawn. The same proceeding can be adopted in soldering the other portion of the coupling into the connecting pipe. If a vertical position is inconvenient for the coupling it can still be soldered in that position, and afterwards twisted carefully into the desired position. In [Figs. 42] and [43], C represents a wood plug for steadying the coupling tail.
Fig. 44.—Soldering Birdcage Wires
Soldering Birdcage Wires.
—For this job, it is better to flatten out the solder to the thinness of brown paper and with a pair of scissors or shears to cut it into very narrow strips. Take little pieces about 1⁄4 in. long, and with the fingers pinch them round the wires just above the joints to be soldered. Touch each joint with a small quantity of killed spirit, and apply the flame of a small blowlamp just underneath the joint; this will cause the solder to run in the joint in an instant (see [Fig. 44]). The flame is quite free from smoke, and does not discolour the wire in the least, as the solder will run long before the wire is red hot. Every joint may thus be neatly made. With a thin piece of copper wire secured in a handle as illustrated, the solder may be drawn any way desired to make special joints in awkward places, where the point of an ordinary soldering bit could not be used.
Sweating.
—In the preceding [chapter] it was shown how useful [sweating] is, when accomplished with the help of the bit. In blowpipe work, also, this method is of much utility, particularly in delicate work where portions have to be joined up in very precise relations. After tinning the joint faces the pieces are secured in accurate relationship with binding wire, or by bolts or screws or other means, or a soldering clamp is employed, having jaws which clamp the pieces and enable them to be adjusted to the exact locations desired, and the flame then brought to bear until the work is hot enough to cause the solder to run.
An example of the usefulness of sweating occurs in the making or repairing of metal name plates having superimposed brass, copper, or other metallic letters. The plate having been flattened and polished and the letters cut out, filed and finished, the backs of the letters must be rendered chemically clean by careful scraping, and are next “tinned” with soft solder. The tinning may be done in several ways, but the easiest is by the blowpipe, using resin oil as flux.
Each letter may be placed in succession on a lump of charcoal, using plenty of the resin oil, and applying the flame of the blowpipe to the surface while one hand holds the charcoal and the other the strip of solder. To prepare the solder, which is sold in sheets by the pound, cut some strips 1⁄3 in. wide. Take hold of one end 1 in. from the end, and with a sharp knife scrape the surface, drawing the knife edge downwards. Do not use the last 2 in. of the strip, as the handling of this part makes it chemically unclean. The greater part of the solder should be about the edges of the letters. The next operation is to solder the letters to the brass plate. As the brass plate also must be chemically clean, the parts where the letters are to go should be lightly scraped. Having ruled parallel lines in order to get the letters in line, lay each down in its proper place, and draw a pencil line round it; then with a scraper just remove the surface of the brass where the letters are to be soldered. A thin piece of solder is now placed underneath each letter, and each in turn is fixed in its place and secured with a loop of binding wire screwed up tight. Nothing now remains to be done but to apply the blowpipe flame and resin oil, when the solder will run underneath the letters. It is better to set the plate on some small lumps of charcoal. When the letters appear to be set fast, remove the plate and boil it in a solution of potash, about 1⁄2 lb. to 11⁄2 gal. of water, and clean in dry sawdust. The resin oil may be made by dissolving resin in sweet oil by gentle heat, until the oil will cause the solder to run.