How to Join Aluminum Tubing

by Sam Smith

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.

Prepare Surface

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.

Weld Joints

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.


  • check Monitoring the behavior of flux and solder is the key to a successful weld. Watch closely. Also, when completing solder on the underside of tubing, it is important to act quickly: Overheating tubing can undo the work already completed on the top half.


  • close The flame of a propane torch can reach temperatures exceeding 5,000 degrees. Use extreme caution and never point toward the face or body. Even several inches away from flame, temperatures remain high enough to inflict third-degree burns.

Items you will need

About the Author

Sam Smith has worked as a professional writer since 2005. His work appears in several publications including "Sauk Valley Newspapers," the Rochester "Post Bulletin" and the "Guardian" of Nassau, Bahamas. Smith received a Master of Science in journalism from the University of Illinois.

Photo Credits

  • photo_camera metal rack with tubes image by Vanessa Pike-Russell from