If an electrically heated solder pot is not available, a small number of wires can be tinned using the following procedure (see figure 2-26):

Figure 2-26. - Alternate dip-tinning method.

• Cut off the beveled section of the tip of a discarded soldering iron tip.
• Drill a hole (1/4- to 3/8-inch diameter) in the round part of the tip about two-thirds through.
• Heat the iron and melt the rosin-core solder into the hole.
• Tin the wires by dipping them into the molten solder one at a time.
• Keep adding fresh rosin-core solder as the flux burns away.

PROCEDURE FOR TINNING COPPER WIRE WITH A SOLDERING IRON

In the field, wires smaller than size No. 10 can be tinned with a soldering iron and rosin-core solder as follows (see figure 2-27):

Figure 2-27. - Tinning wire with a soldering iron.

Select a soldering iron with the correct heat capacity for the wire size (see table 2-3). Make sure that the iron is clean and well tinned.

Table 2-3. - Approximate Soldering Iron Size for Tinning

Start by holading the iron tip and solder together on the wire until the solder begins to flow. Move the soldering iron to the opposite side of the wire and tin half of the exposed length of the conductor.

The tinned surfaces to be joined should be shaped, fitted, and then mechanically joined to make a good mechanical and electrical contact. The parts must be held still. Any motion between the parts while the solder is cooling usually results in a poor solder connection, commonly called a "fractured solder" joint.

Q.25 What causes a "fractured solder" joint?