I really like the utility and look of these lunchboxes, so I wanted to try making my own. Tuna cans seemed like the perfect compartment -- the only problem was getting them to nest nicely. I was really impressed with how well the can-shaping jig worked. It pulled in the bottom of the can and made a uniform ring just above it. After that, the cans fit together really well, and all I had to do was add draw catches and sand everything...and eat the tuna.
Step 1: Make the Can-Rolling Jig
Building the jig is very easy. In a piece of scrap 1x1 wood, drill two holes to accomodate the hinge pin shafts. Space these holes so the pins are roughly parallel when the heads are nested. Slip the hose clamp over the pins and stick them in their holes.
The top pin will stick out further than the bottom on account of the heads being nested. If everything works out, this should be enough so you can clamp the vise grips to the top pin and turn it through a complete revolution. You may want to trim a bit off the bottom shaft to give yourself more room to work.
Use a vise to clamp the wood and hold the whole thing steady. You're ready to roll.
Step 2: Prepare the Cans
Step 3: Make the Lid
Step 4: Make the Draw Catches
To solder the draws, first shape them to follow the curve of the can. I hammered the draw on a wooden dowell to get the rough shape. Once the draw and can fit together well, clean both surfaces and apply flux. I held them together with vise grips and used a torch to heat them to soldering temperatures. The inside of the tuna can has a protective coating that will burn off if you heat it too much. When you're finished it will probably look ugly, but have faith in the power of wire wheels and sandpaper!
With both draws in place, we need to fashion the catches. I used welding rod for mine. Take a long piece and fold it in half (both halves should be taller than the tiffin box). Using pliers, bend the fold over to form the hook. On the other side, form a sharp inward bend on each rod. I used the vise to help with this. Once the welding rods are shaped, trim them up and hook them into the draws.
The draw catches should hold the stack together tightly but not pull so tightly that the cans deform.
Step 5: Finishing Touches
Last but not least, remember to re-wash the cans really well before use. I don't make any guarantees about food safety -- tuna cans are certainly food grade, but when you heat them, strange things can happen. Keep that in mind as you are washing and scrubbing those cans.
Go have a picnic and post pictures!