Q&A for How to Bend Sheet Metal

You can use a bending seamer, as well as form blocks that are made of metal or hardwood that are used with a mallet.

There isn't really a minimum. Thinner aluminium bends easier, just like steel, but you also want structure (so it holds its shape). So your best bet is to buy something like 0.5 mm and 1 mm and give it a go, going thicker if you need it to hold shape better, and thinner if it isn't bending to shape very well. However, thicker sheets are more prone to cracking, and then there are different grades of aluminium, so you will need to buy the right grade for the job too.

Did you size the sheet of metal to take into consideration the stretching of the metal at the bend? If you do a 90-degree bend, the metal will stretch and shrink the thickness of the metal.

When it is dull red, it's easier to bend; bright red/yellow is optimal.

Yes, it will make it easier to bend it.

That depends on how you want to bend it. If you want to bend it, in an elbow like a piece of pipe, that isn't going to work as the wall of the can is too thin. The can will collapse under any kind of bending operation. Unlike a pipe which derives its strength from the thickness of its wall, aluminum cans actually get their strength from the non-compressible liquid sealed inside them. However, an aluminum can could be cut into pie wedges and welded back together in the form of a segmented elbow (like those used for vent pipe) if you really, really need one. There's plenty of welding videos for aluminum cans on YouTube.

Apply an equal amount of force used to create the crease in the opposite direction of the crease. Yup, easier said than done. Once a piece of sheet metal is creased, its well neigh impossible to take the crease completely back out of it. In smaller pieces, I've had success tinkering out a crease with a hammer and a dolly, or on a hydraulic bench press sandwiched between two pieces of flat bar. In a large sheet, a long piece of flat bar could be used as a dolly and some careful tinkering, but the crease will almost always be noticeable. I used a forklift once to flatten out a piece of sheet with mixed results. Next time I'd want to sandwich the sheet between some flat bar first.