Intro: Tiffin Box From Tuna Cans
A tiffin box is a small lunchbox used to carry a tiffin, or light meal. The lunchbox consists of a stack of steel or ceramic compartments for each food item. According to wikipedia, the term originated in colonial India, and today in Mumbai there exists a complex network tiffin-boxed lunch deliveries on a massive scale.
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
The can rolling jig consists of two old door hinge pins and a hose clamp. The heads of the hinge pins nest with each other. By applying pressure with the clamp and rolling the can, we can raise a lip on the can's side. Check out the embedded video in the next step to see it in action.
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
Mark one of the rolled cans evenly all the way around and cut it with the dremel tool. Make sure to sand the cut edge smooth on the rolled half. To make it fit inside the top compartment, crimp the lid using the stovepipe crimper. Start conservatively and crimp deeper until you get a good fit.
Step 4: Make the Draw Catches
The draw catches will hold the stack together when in transit. The draws get soldered to the bottom compartment, and the catches are sized to hook over the rim of the lid.
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
At this point, the Tiffin box is operational but probably doesn't look too nice. I was really happy with how quickly the surfaces shined up after I used the wire wheel on my bench grinder as well as good old sand paper and elbow grease. As always, start with coarse grit and move towards fine grit.
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!