Sheet Metal Brake
My rocket stove heater needed a heat exchanger. The obvious choice was to construct it out of sheet metal. Doubly obvious because there were a bunch of discarded BBQs that I could scavenge sheet metal from! So, again obviously, I needed a sheet metal brake.
My initial plan was to just construct a plain brake at a suitable size. When I went to the tickle trunk to see what I had on hand, I found all these 2-inch by 1/4-inch thick aluminum angle cutoffs from a previous project, so I upgraded my plans and decided to make a pan brake. The difference between a plain brake and a pan brake is quite simple. A plain brake can bend only opposing edges while a pan brake has slots or other ways to make room for adjacent edges that have already been bent. Since all I had was cutoffs, there was very little additional effort to make a pan brake. A bit of math (yay spreadsheets!) and I figured out all the various lengths and positions I needed to make a pan brake that could handle everything from 1 inch to 24 inches in 1-inch increments without having to add or remove teeth. I wasn't sure that the aluminum was really up to the task, but so far the only problem I've encountered is that my clamping bar isn't stiff enough to generate the force I need to get really clean breaks. It was good enough to get me through the building of the heat exchanger and I have both solid steel bar stock and 1.5-inch round steel tubing that should be up to the task when I decide to tackle an upgrade.
In the foreground, you can see my first test, a small pan made out of steel flashing to keep things from rolling around on the bench.
For the curious, that big gooseneck thingy sticking out of the bench is called a holdfast. Drop it into a hole in the bench with the flat end on what you want held down, then whack the bend down with a mallet. Friction created by the clamp levering against the hole keeps things solid. Knocking the back side of the bend with a mallet releases it. Quick, simple, flexible.