Heavy wires which must be connected to a terminal of a large switchboard or other electrical apparatus are soldered to lugs for convenience in fastening. Many lugs are soldered to wires without the wire touching the metal of the lug, the only connection being the solder. In Lesson 9 it was stated that solder is not a good conductor of electricity and when soldering wires to a lug the wire should be wrapped around the lug tightly. In the case of a heavy wire the hole in the lug should be just large enough so the wire will fit without any forcing after the insulation has been removed. There should be a space of about 3/16" between the end of the insulation and the lug when the wire touches the bottom of the hole in the lug. The wire should be placed on a hard surface and hammered a little out of round so that it will have to be forced into the lug. This will assure at least some direct contact between the two copper surfaces. Both the wire and the lug should be cleaned before the wire is forced into the lug. Electricians usually use soldering paste for this work. Do not use too much paste and after the soldering is finished wipe off any excess paste between the lug and the insulation. Before the sweating is started a few layers of friction tape wrapped over the insulation at the end will prevent the insulation from fraying. The tape can be removed after the lug has cooled completely. The sweating is done the same as on copper tubing. Figure 14 shows the set-up of lug and wire.

Setup Of Lug And Wire

Figure 14.

Solder Used For Holding Work

In the workshop there is sometimes filing or turning to be done on small work which cannot be held conveniently. By tinning and sweating the work to a larger piece of metal which can be held in a vise or lathe such jobs as filing, lathe turning, engraving and many others can be held securely. After the work is completed reheating will release it and the excess solder can be wiped off with a cloth or brush. The procedure is shown in Figure 15. If the work is not too large this sweating can be done with the soldering copper.

Holding Work

Figure 15.