Commercial boxes for electronics projects are expensive. You can spend more on the enclosure than you spend on the parts it protects, in many cases. I’ve seen plenty of ideas for cheap enclosures from hardware store products. But I have a source for cheap project enclosures that’s both cheaper and more versatile.
Tin boxes, available at dollar stores and gift stores especially in the fall and winter seasons and in secondhand stores almost year-round, make sturdy and inexpensive enclosures with lots of space inside. They are comparable in size to commercial project enclosures but cost 1/3 as much. And if you know where to shop, you can get them year round at an even lower price.
Cheap project enclosures from tin boxes
Gift and craft stores sell rectangular tin boxes in the fall and winter months. They’re sometimes called cookie tins, because people will put candies or homemade cookies in them and give them as gifts. People call them tins, but they aren’t 100% tin. They are actually steel with a tin plating to inhibit rust, just like the cans in the vegetable aisle of your local supermarket.
Sometimes the tins are bare metal with a clearcoat, but usually they have a seasonal lithographed design on them. If you want a solid color, the tins take paint well. Paint it with a couple of light coats of spray paint — here’s how — and you can make it look how you like.
The tins usually sell for around $5, so they are much cheaper than commercial plastic project boxes. Using electrical boxes from your hardware store can be slightly cheaper, but a gift box tends to be larger, and I think they look nicer.
Plastic enclosures have the advantage of not being conductive, but this also means they don’t dissipate heat well. If you have electronic components inside, it’s nice to use a metal box to help keep things cool. I prefer to use a metal box and just insulate it where needed.
Preparing your tin box as a project enclosure
The coating on the metal isn’t a great conductor, but you should always assume the box is conductive. You’ll want to insulate any sides that are near any components, or at least put a nice air gap between the sides and your electronic or electrical components. You’ll also want to ground the case to protect against any shorts electrifying the box.
The metal on these is pretty thin, so it drills pretty easily. You can tap the holes to take screws as well, but you’ll need small screws and a fine thread. My success rate tapping them for 6-32 screws is around 90 percent, but 6-32 is nice because it lets you use computer case standoffs to hold your circuit board. If you strip the thread like I seem to do 10 percent of the time, just secure the standoff on the underside of the project with a 6-32 nut, and use some threadlocker to hold it in place. If you don’t overtighten, you’re less likely to strip the hole. Just screw it in snug, and if you want it really secure, put some threadlocker in the hole first.
If you don’t need to use standoffs, you can use other sizes of small screws. 4-40 would work well. In metric sizes, M3 is about as large as you’d want to go. M2 and M2.5 would work well.
The lids usually snap on. To secure them, you can attach the lid, then drill through the side and tap it for a 6-32 or smaller screw. And when you have two layers of metal, you’re less likely to strip the thread.
You can use a screw tap, but if you don’t do this often, you may just want to buy a box of thread cutting screws.
Avoiding burrs in your project enclosure
When you drill large holes, you’ll end up with a burr on the end. To reduce burrs, drill a small pilot hole, the same size as you would use for a screw, then drill the hole progressively bigger. Starting with a 1/8-inch hole then progressing up 1/16 at a time to a half-inch hole works well for me to run thick cable into the enclosure. Drill the hole a bit oversize and press in a rubber grommet to protect the cable. After you run the cable into the case, tie a knot in the cable to keep it from pulling back out. I’ve seen people question the effectiveness of this, and whether it’s the right way to do it, but a knot is more effective than a wire tie.
Sourcing tin boxes inexpensively
These tin boxes frequently turn up in secondhand stores like thrift stores, especially in November as people start getting out Christmas decorations. People tend to save their tin boxes a number of years and donate them with their old Christmas decorations they don’t use anymore.
Tin boxes also turn up at estate sales very frequently. I almost always find a big cardboard box full of tins in basements. Or sometimes there’s a shelf full of tins down there.
Circular tins are more common, but if your project needs a rectangular box, it seems like there’s always one or two rectangular ones in a stash of tins. If you don’t mind a circular tin, you can expect to have a wide selection.
Prices at estate sales and thrift stores tend to vary, but I’d paid as little as 25 cents apiece for them, and as much as a dollar. I won’t go to an estate sale just to look for tins, but I don’t have to. I go to sales looking for tools, vintage computers, or vintage trains, and frequently find tins at those same sales anyway.