A soldering iron supplies "cold" heat to metal parts that need to be joined. The completed joint bonds the parts to form an electrical connection between wires and metal parts. A chemical cleaner prepares hot surfaces for molten solder, an alloy (tin combined with lead) made of non-ferrous (or "iron-free") metals. The melting point of these alloys ranges between 364 to 460 degrees F (183 to 230 degrees C). A soldering iron is actually a very small blow torch.

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Soldering Galvanized Sheet Metal

Always wear eye protection and gloves when soldering or using any soldering materials and chemicals. Non-corrosive flux (a chemical used to assist with heat transfer from heat source to metal surface), such as ruby fluid or diluted hydrochloric acid, is used to solder and fuse galvanized sheet metal. To make a tough joint, the metal should be locked together or riveted no further than three inches apart.

Soldering in Plumbing

Some equipment relies on a supply of cold tap water. Shut down any equipment that is affected by shutting off the water supply. Be aware of flammable materials near your workspace. Copper pipe fitting has a very small gap between the two pieces when soldered. The solder forms a seal and makes a watertight joint.

Arts and Crafts Projects

Soldering is used for hundreds of arts and crafts projects and is a process used by do-it-yourselfers from all walks of life and hobby-working desires. Learning to solder is easy and those who make everything from jewelry and sculptures to their own musical instruments and stained glass use it.

Soldering Stained Glass and Mosaics

It is said that it's best to use lead-free solder for making stained glass windows and mosaic sculptures. The basic tools for making stained glass include safety glasses, a glass cutter, pliers, a glass grinder, copper tape, solder, flux, a 100-watt soldering iron, the glass pattern, the actual glass and a solid wood work surface.

Forming Permanent Circuit Board Connections

Contact between two wires is used in order to establish electrical continuity between the two metals. Prevention of a clean contact between metal surfaces (dirt, dust, oil, corrosion, missing insulation, etc.) inhibits continuity. Electrical wire is insulated and the insulation cannot be removed or stripped when establishing bare metal-to-metal contact. Soldering "locks" the wiring down to the circuit board.

Soldering Copper Pipes

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Copper tubing should be cleanly cut and dirt and corrosion should be cleaned off the pipe ends with an emery cloth until the copper shines. The inside should be cleaned with a special wire brush, but should not be touched with bare hands. Brush flux over the metal surfaces to be joined, on the inside and out; then wipe off the excess. Heat the joint with the soldering iron or a propane torch, moving the cone back and forth for even heating. Fittings may require higher heat (700 to 800 degrees F) in order to bring the solder to the melting point. Avoid over-feeding the joint in order to avoid clogging the tube. The solder hardens as it cools.

Car and Engine Repair

No soldered joint is strong, so it can't be relied upon for strength. Materials are generally soft and pliable (malleable) and used only to fill up irregular places, smooth rough surfaces, or make tighter joints. Paint, grease and dirt must be removed. The most common flux for car repair is muriatic acid, which is dissolved with zinc. Solder is used to tin the edges of metal sheets and fill up holes.

Home Projects

Soldering pencils, guns and irons that are adequate for home use are made in abundance. Most are heated electrically and have tips that can be used with a propane torch. The proper tool depends on the project, but tasks like joining wires and circuit-board repairs, may call for varying amounts of heat or more control. As with other soldering projects, tool tips must be thoroughly clean at all times.

Soldering Jewelry

To solder jewelry, you will need the metal (such as sterling silver wire or pewter, etc.), a torch, a soldering pick, Borax flux, a pickling agent, silver solder, posts or hooks as needed, wire cutters, thin copper wire and tweezers. Other items you may need are sandpaper, a polished hammer and anvil or planished silver.

Soldering Vacuum Tubes

Inexpensive vacuum switch tubes are soldered to form a sealant and to insulate housing parts in metal to ceramic connections. For example, copper parts can be soft-soldered to ceramic without risking the tube. Silver tin solder is placed on a pre-fab vacuum switch tube to form a corrugated ring with a cover that forms a tight vacuum on the circuitry board to which the tube is attached.