Cardboard Mini Combo Safe
Introduction: Cardboard Mini Combo Safe
Locks and safes are very common in this modern world, when almost everything valuable needs to be kept secure. Obviously, cardboard isn't the best option as a holder for a very expensive item, but it can be cool to have. In this tutorial I will show both how a combination lock works and detail the steps I went through to make this cardboard "prototype".
Supplies
The supplies for this project are definitely on the cheap side:
-cardboard boxes (double corrugated is better for more strength)
-standard printer paper
-elmer's glue
-hot glue sticks
-pencil
-cereal box
-q-tips OR toothpicks
Optional Supplies:
-super glue (only needed if you want good durability)
-resin (I didn't do this because of time and budget constraints)
Tools:
-box knife
-hot glue gun
-pencil/pen/sharpie
Important note: If you want to make this out of wood, it would be be exactly the same process. Just swapping the cardboard with wood would be a great choice if you want extra strength. The only reason I chose cardboard was because I am on a budget and don't have much choice. You could also coat the cardboard in a few layers of resin to make it as hard as a rock.
Step 1: Outer Shell
The outer layer is pretty easy to make. I started by cutting two 5''x5'' squares of cardboard. I then cut two 4.5''x5'' pieces and hot glued all four together. Try to be as neat as possible for a decent aesthetic later on. It is pretty self explanatory how these all go together.
Next, cut four 4 1/4''x5'' squares. Later on, these will be lined upon the inside to double layer the whole box. However, I wouldn't do it yet because on one square you still need to cut a small section out that the bolt will rest in.
Step 2: Combination Lock Mechanism
The standard design for combination locks revolve around discs. Basically, there will be three small circles, the discs, on a cylinder that are able to freely spin. On each disc there is a tooth that will meet up with the other disc when the dial is spun a few times. Each disc also has a notch in it. Only when all three notches are lined up can the lever fall into the notches and pull the bolt out. This video explains the whole mechanism in detail, although for my safe there are a few modifications.
Step 3: Building the Lock
You'll want to start out by making the cylinder that the discs rotate upon. This is done by taking paper and wrapping it around a pencil with Elmer's glue. 622
Don't glue it to the pencil, but glue the paper so that it is a decently hard cylinder that the pencil can spin spin freely inside of. Next, cut out three circles from cardboard that are a bit over an inch in diameter. The measurements don't matter two much in this combination mechanism, just make sure it will fit in the final box. Punch holes in two of the circles that will allow them to slide onto the paper tube. You want a little bit of friction but not too much or it will hinder the ability for the discs to rotate. On the third disc, punch a hole the size of a pencil, which should be slightly smaller than the paper tube.
Now add some teeth to the outer rim of each disc. Make sure it extrudes no more than 1/4''. Use the photos above for reference. In the end, when you rotate one disc, it should meet the teeth of the other discs until all three spin. Note that the middle disc should have two teeth, one on each side. Cut a notch into each disc with random placement so the combination will end up random.
Now take some thin cardboard and cut it into strips 1/4'' wide and long enough to be wrapped around the paper tube. These are the sections that separate the discs seen in the pictures above. Slide two discs into place along the tube, 1/4'' apart, and glue the cardboard strips in between the discs to separate them and keep them in place. The third disc needs to be glued to a section of the pencil. The pencil should extend long enough to go through the wall in order to attach the main dial. In my reference pictures, the pencil is green.
If done correctly, spinning the end of the pencil, which is attached to one disc, will eventually spin every disc as the teeth meet up. You can now try lining up the notches.
Step 4: Lever
This part is slightly difficult to get right. It takes a lot of trial and error to get the right shape. It is sort of like a more slanted 'L'. 276