[voxleone]

What about aluminum? I haven’t been able to find a welder willing to work on my custom bike frame, so I’m considering learning to do it myself after taking a welding course. The custom car builders on TV make it look easy, but aluminum seems like an incredibly difficult material to work with.

[ssl-3]

It's difficult find a welder willing to work on an aluminum bike frame not because aluminum is hard to weld. It's not so bad to stick two pieces of aluminum together in a new-to-them way with the right tools as long as maintaining the original strength isn't important.

But strength is important for bicycles. And aluminum bike frames are already built down to a given weight -- they don't have much in the way of extra strength to lend.

The heat of welding permanently changes the way the surrounding metal works. That's not ideal for safety devices like a bike.

Heat treatment can be done later (and is done when aluminum frames are built), but that's a different process to learn and it's pretty far beyond the gamut of what most welders are willing to deal with. Most welders don't have the bike-sized oven that's needed, let alone the training and experience to get it right, and with a sample size of exactly 1 it's a risky operation. It's easy to get things like warped tubes out of this process and turn a beautiful piece of wall art into scrap metal.

[83]

If you get a quality tig welder aluminum isn't too bad. It's definitely more difficult than steel but I taught myself to weld AL without too much trouble. Practice on some scrap for sure before your bike - it'll be easy to blow a hole in thin bike tube.

The biggest challenge I've had in welding aluminum as a hobbyist is that I rarely know what aluminum alloy I'm working with. Most things don't say what type so we're left guessing what filler is appropriate. If you use the wrong filler it could be prone to cracking again in the future.

Also for thicker aluminum preheating is very important. The aluminum transfers heat away very quickly so you get cold lumpy welds if you don't have both parts pretty hot at the start.