Although the opportunities to use a soldering iron to make a home repair are limited, we nonetheless recommend including a small soldering tool and a tiny roll of solder in your home tool kit. With just a single repair, a soldering tool can save you more than 10 times its cost.

The speakers in every radio in your home are solder connected. There are solder connections in your television, telephone, computer, stereo, VCR, boom box, dishwasher, range, oven, refrigerator, small power tools, blender, food processor, toaster - you name it. Everything in your home that uses electricity normally will have at least a couple of soldered connections. Small appliance repairs start at $25. A soldering iron and a small roll of solder can be purchased for less than $6. Although you can spend $35 or more on soldering gear, chances are you won't need such fancy equipment. The one we have cost $12.

Soldering is a process where molten metal is used to join metallic surfaces. We will discuss soldering copper wires, the kind used in common household tools, appliances and electronics equipment. Silver soldering and other types will not be covered here.

Everything you need to know to make a good connection can be found in this column. Soldering is one of the simplest do-it-yourself projects we know of. No heavy lifting, no confusing nailing patterns and no rule book or help manual. It is as easy as 1-2-3:

1) clean the wires so they shine,
2) twist them tightly together and steady the connection with clamps, and 3) heat one end of the connection with the tip of the soldering iron. After a moment or two, touch the other end of the connection with the solder. Continue to hold the soldering iron against the wire. The heated wire will melt the solder and it will immediately begin to flow toward the end of the connection being heated by the soldering gun.

Molten metal will always flow toward the heat source. When the solder reaches the gun, the connection is made. The most difficult part is holding everything still long enough for the solder to cool (a few seconds). For clamps, try a clothes pin or two, a pair of tweezer clamps or a small pair of vise grips.

There are several ways to clean the wires. Remember, all of the wire to be soldered should be bright and shiny clean - not just the tip of the wire - all that is to be soldered. Solder will not stick to a dirty surface. Sandpaper, emery paper, steel wool, a file or a pocket knife can be used for cleaning. Since a razor knife always can be found in our tool pouch, that's what we use. We lay the blade on the wire (perpendicular to it) and wipe the sharp edge along the length of the wire. Corrosion, discoloration, and everything else comes right off. Spin the wire and continue to scrape until it shines all the way around. We find a tiny file more handy than sandpaper for cleaning terminals and connection posts. Sandpaper has a tendency to leave a granular mess inside of some items. You might have to vacuum when you are done.

With everything cleaned, the wires can be twisted together, or a wire can be looped through a terminal and then twisted around it. The idea is to secure the items being connected before soldering begins. Clamps are then used to hold the connections still during soldering. Twisting the wire together also adds strength to the connection.

With everything cleaned and clamped in place, you then melt the solder. Whatever you do, don't melt the solder with the tip of the soldering iron. The connection itself is heated by the soldering iron and the hot connection melts the solder. When the contact between the soldering iron and the connection is broken, the connection cools and the solder begins to harden. Once the solder hardens completely, the connection is complete. Since solder always flows toward the source of the heat, the joint will be much stronger if the tip of the soldering iron is held at one side of the connection while the solder is held to the other.

The best solder for electrical work is 60-40. Sixty-percent tin and 40-percent lead. Before a joint is soldered, a coat of flux must be applied. Flux is a paste that helps remove any remaining tarnish or corrosion. It also helps the molten solder to flow freely. For best results, do not use acid-core flux when making electrical connections. Rosin flux is what you want. Better yet, purchase solder with a flux core and kill two birds with one stone. Ask for resincore 60-40.

Finally, keep your soldering iron (or gun) in good condition by being sure that the tip is clean and tinned. Tinning a soldering iron tip is easy. Sand or file it until the copper shows through. Then heat the iron and touch the hot tip with fresh solder. It takes only a tiny amount. Let the iron cool and store it for next time.