Nuts and Bolts + Cardboard = Awesome (in 5 quick steps)

Cardboard  is widely available, inexpensive, lightweight, and relatively strong. It’s a fun and easy building material, but it can be difficult to fasten to itself (or other materials) strongly.

In order to solve that problem, we turn to a reliable technology that hasn’t changed much in more than a century: steel nuts and bolts. We use 8-32 nuts and bolts (8-32 describes the size of the thread), but many dollar stores and all hardware stores have some nuts and bolts and you don’t need to be very particular about size.

1) Gather your materials

If you want to use the same ones as us, we usually order ours online, and if you do too, a good source is McMaster-Carr. Our machine nuts are part no. 90272A199, wingnuts are part no. 90866A009, locknuts are part no. 90631A009, washers are part no. 90313A102, and 1” bolts are part no. 90272A199.

2) Punch some holes

By making holes of the appropriate size, you can pass a bolt through cardboard and hold pieces together really well. We use a hole punch with a few different size choices on it. (Hole punches of this type are for sale at some hardware stores, or from McMaster-Carr part no. 3488A9.)

If you don’t have a punch handy, you can also use a sharp pencil. WARNING: if you’re using a pencil to make the holes, be very careful! Always put the cardboard flat on a table with some scrap cardboard beneath it and push straight down with the pencil.

3) Start making connections

To use this method to connect pieces, simply make a hole that the bolts you’re using can juuuust fit through. (If you make too big of a hole your connection will probably have some wiggle in it.)

The nuts and bolts are small, but they’ll be able to squeeze in on the cardboard quite hard when you tighten them. To reduce the chance of the nuts and bolts tearing through the cardboard, use washers between the head of the bolt and the cardboard, and also between the nut and the cardboard.


4) Adjust your tension

If you tighten the nut onto the bolt, you’ll be holding your cardboard together really strongly. But if you leave it loose, the junction will work as a swivel. The choice, of course, is yours—do you want those two things to be stuck firmly in one position, or do you want them to move like this:

If you want to keep the connection loose (so it can swivel freely), either use a locknut, which has a piece of nylon in it so it’s hard to turn on the bolt, or if you don’t have any locknuts, you can use two regular nuts tightened against each other to do the same thing:

5) More ideas

…and finally, if you want to be able to adjust the holding power of the joint frequently, you can use a wingnut, which is designed to be easy to loosen or tighten by hand.

If you have longer bolts, you can stack up a lot of pieces of cardboard and start making really strong swiveling things like this robot arm!

That’s it! Go make something awesome!

6) Optional printable hinges

And finally, if you have access to a 3D printer, you can also extend your cardboard creativity by making yourself some nice hinges we designed, listed as Thing 39137 on Thingiverse. It’s designed so that an 8-32 screw can be used as the pintle, and we’ve found our prints are fairly strong. (The hole in the face of the hinge is meant for easy mounting with a bolt to your cardboard, but the hinge may also be hot glued onto a surface.)