Soldering, Brazing and Welding

by Unknown

Fig. 16.—Tinning Bit in Sal-ammoniac Block

Let the bit-faces be made shapely and filed bright and the tool thoroughly heated in a clean fire, removed, flicked free of ash, and then held down firmly in the cavity of the sal-ammoniac block (see [Fig. 16]). Profuse white fumes will arise, and the surface of the salt will fuse. Bear heavily on each facet in turn, and then melt a few beads of solder into the cavity along with the bit, and the latter will become brightly tinned in a moment or so. The bit should be applied to the “ammonia block” every few heats, or as required, as the work progresses, and flicked with a tuft of dampened cotton-waste.

The sal-ammoniac has one great disadvantage—it is deliquescent (collecting moisture from a damp atmosphere), and its near proximity to most metals oxidises and corrodes them. Iron and steel, particularly, it rusts rapidly and deeply. Therefore the tools (saw and chisel) used to shape the block must be washed, dried, warmed, and greased before they are laid by, and the waste fragments must be carefully swept up and disposed of. The block itself must always be kept apart from tools. Plumbers enclose it in a sheet-lead box wrapped in a greasy rag; amateurs may store it on a dry shelf, parcelled in waxed paper secured by a rubber band, or in a length of motor-tyre inner tube, rolled up.

Simple Soldering.

—Scrupulous cleanliness in everything connected with the process of soldering is essential to success. The ordinary procedure in making a joint is to clean the surfaces first by filing or scraping with a scraper or a knife or a plumber’s shave-hook ([Fig. 17]). In some cases, dirty metal is cleansed with dilute hydrochloric acid. With or without preliminary heating of the work, flux is then applied to the joint, and the heated bit is held in one hand and a stick of solder in the other, and the stick drawn along the joint while the bit touches it (or “drops” of solder may be transferred to the work by means of the bit). This will cause a line of molten solder to run, and some skill and care are necessary to get just the right amount of solder without wasting it and allowing it to spread in a lumpy fashion beyond the necessary area. The bit is next worked up and down the joint to spread the solder, and by the transmitted heat to make it thoroughly penetrate the joint. This is an outline of the process, and there is a number of points requiring special instruction or a few words of caution.

Fig. 17.—Shave-hook

Note that the work must be filed, scraped, or otherwise mechanically cleaned, and then chemically cleaned by coating with the flux just where the soldering is required. In heating the copper bit do not let it reach even a dull red heat. Lightly dip it into the flux to clean the point; then, with a small button or blob of solder resting on the work, place the bit momentarily upon it to cause the solder to flow, and draw the bit where the solder is required.

Many beginners try to draw along the solder with an insufficiently heated bit. The result is a series of lumps—“putting it on with a trowel,” as it is sometimes termed. A good joint cannot be made this way, however much solder may be used.

Some beginners fly to the other extreme, and try to make a neat job with a red-hot bit, which results in the solder assuming a sandy appearance and in the work being discoloured.