Lightweight and durable, aluminum tubing forms the skeleton for items such as performance bicycles and commercial airliners. It also forms the vacuum lines in some cars and industrial equipment. It accepts and dissipates heat quickly, making it a good electrical conductor. Tubing is joined through a welding process known as soldering. Most aluminum tubing is rated to 30,000 pounds per square inch (psi) of pressure, which makes it ideal for high-pressure or high-flow applications when copper won't do. It also resists corrosion better than copper, making it more suitable for transfer of chemicals.
Measure and cut the tubes to the desired length using a chop or hack saw. Be sure to account for depth in joints that will be welded later.
Drag the metal file over cut ends or rub them with emery cloth to remove any burs and dull the edges.
Press the joints onto tubing by hand, then strike them with a rubber mallet until you have a snug fit.
Ignite the propane torch and turn it to the highest setting. Note that depending on the torch, this may require a source of spark--a flint or match will do.
Place the inner tip of the flame over center of the joint. Drag the flame back and forth and side to side over the joint for about 15 seconds.
Dip the aluminum solder rod into flux, then rub it over the seam. Apply liberally: Extra flux will not affect the quality of the weld. Continue to wave the torch over the joint with one hand while applying the flux.
Observe the behavior of the flux: Once it starts to wick into seam, the joint is the proper temperature to accept solder.
Drag the tip of the solder rod over the seam and observe its behavior. If the solder bubbles up, the tubing has cooled and needs more heat. If the solder draws into the joint, turn the tubing over and repeat. Note that tubing will be hot. Use pliers or heat-resistant gloves.
