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Soldering is a process whereby an alloy is fused and applied to the joint between metal objects to unite them. It is used to join all types of metals in sound equipment, toys, hand held appliances, televisions and much more. The two most important things to remember when you are soldering are to clean and in most cases, heat the metal, not the solder.
Any metal you plan to work with when you solder should be free of any rust, grease, moisture, tarnish, dust or dirt. With the exception of working with stained glass the metal should be hot enough to melt the solder and boil away the flux. Flux is a substance that cleans the metal and prevents oxidation. It will also help the molten solder to flow and adhere to the metal. Most solder can be found in spools of hollow wire with rosin flux or acid flux in the center of the wire. If you are soldering zinc or galvanized iron use acid core solder. For copper plumbing and such jobs it is best to use solid solder and apply the flux separately. To do this you will need to cut your copper pipe with a tubing cutter by screwing the cutting wheel against the pipe and rotating the cutter. Each time you make a little turn, tighten the screw until the pipe is severed. When joining the pipe to a fitting the end and inside end of the pipe will need to polished with steel wool. Clean the inside of the fitting as well. Using a soldering paste of non-corrosive flux apply to both the pipe and fitting. Insert the pipe and turn it to spread the flux. Then holding a solid core 50-50 solder to the joint, heat the fitting with a propane torch until an even bead of solder appears around the joint. This may take a second since the solder will be drawn into the joint.
With all metals you are soldering, heat the metal with a soldering gun, soldering iron or propane torch. The soldering gun works with a trigger, heating and cooling very quickly. The soldering gun is best used for electrical soldering and other fine work. Most soldering irons come in many different sizes and can be purchase for large or small jobs. Like the soldering gun they can be plugged into any wall outlet. The different sizes make them convenient for any size job you are soldering but be sure you get the correct size. For larger jobs a propane torch should always be used. Most propane torches burn propane gas at 3,000 degrees Fahrenheit. They should always be used to sweat solder such things as copper water lines or to do other heavy soldering. The main components of a propane torch are the valve body, orifice tube, burner tube and burner head. All of these parts are made of brass or steel, even though you can purchase a less expensive unit that has aluminum parts. To use a propane torch you should screw the body onto the mouth of the fuel cylinder. When you do this the valve body will puncture the self-sealing valve of the fuel cylinder. Turn the handle to the valve body one-quarter turn to get the propane gas flowing properly through the torch. Then turn the handle back to reduce the gas flow and ignite the opening of the burner head. It is best to light a propane torch with a flint and steel spark maker. A standard head on a propane torch will make a pencil size flame. Before you begin you should give the handle a half turn to increase the flame. Most propane gas cylinders will last between 10 and 15 hours if you disconnect the torch from the cylinder between uses. Always allow a propane torch to completely cool before attempting to remove the valve body.
If your job is smaller or if you prefer to use a soldering iron or gun, be sure to file each face of the tip smooth and then clean it thoroughly. Heat the iron or jun and hold a rosin core solder to the tip until it is covered with a coat of solder. Use a damp sponge to wipe away any excess. If you are soldering a joint you will first need to clamp the pieces together to hold them in place. Next you should heat the surface from below if possible and apply the solder from above. The solder should melt on contact and run into the joint you are soldering. It is wise to remember that melted solder will always move toward heat. When the solder is finished, wipe away any excess flux with a damp sponge. When you are joining two flat surfaces you will need to clean and flux the surfaces you are joining. Heat each separate surface with a torch and add a thin, even coat of solder. All the metal to cool and then clean the surfaces again. Add flux to both surfaces and clamp them together. Reheat the two surfaces until a thin line of solder appears along the seam. When the metal has cooled, wash away any excess flux.
Sound equipment, hand held appliances and toys that have wires soldered to terminals can be re-soldered with a soldering gun or soldering pencil. You should use a rosin core solder for this purpose. Begin by cleaning the wire and terminal with a very fine sandpaper or steel wool. Hold the wire to the terminal and apply solder at the junction. Then place the tip of the soldering gun to the underside of the terminal until a bead has formed. Continue holding the two together until the solder has hardened. As a safety precaution when you are working with solder you should wear gloves and goggles. Try to find a thin but non-absorbent type of glove for small jobs that will allow you to use your fingers if necessary. Always work in a well-ventilated area and when using a torch, be sure your tank is not leaking. Propane gas has a very distinct smell so you should be able to detect it with no problems.