This tutorial show you how to made a Safe Box with Combination Lock from Cardboard. Follow the following steps in this instructable if you want to repeat and watch video to enjoy :)

Materials and Tools :

- 2 x Cardboard 50x80cm

- 1 meter x Tube PVC diameter 12mm

- 2 x Pop-sticks

- Hot Glue sticks

- Metric ruler

- Pencil compass

- Pencil

- Cutter Knife

- Hot Glue Gun

- Brush

Step 1: Making Gears Wheel

First, cut the cardboard according to the following forms:

- 3 circles of diameter 80mm,

- 1 circle of diameter 60mm,

- 1 rectangle 12x260mm

Then they are glued perfectly superimposed following the same axis.

To mount the gear teeth, I remove an upper layer of the rectangle and glue the other part to the perimeter of the gear body.

We need a total of two gears wheel : the first to convert the rotational movement into a translational movement. the second is used to reverse the direction of rotation

Step 2: Shaping the Safe Door

Using a cutter, we start by cutting the outer frame size 34x42cm and then cut the cardboard to form the door size 25x31cm.

Step 3: Making the Holes

To make all the holes needed in this project, you can simply use a pencil. Holes are required to enter the axes of rotation of the gear wheel and the other lock wheels.

We need a total of 3 holes in this project

Step 4: Fixing the Gear Wheel

Using a cutter, we start by cutting two 20mm pieces of pvc round tube. The pvc tube is 6mm in diameter, it is the axis of rotation of the two gears wheel. The first gear is glued to the upper gear and the second is glued to the safe door. The glue to use is hot glue.

You have to pay attention to the alignment of the two gears.

Step 5: Building Tongues Lock

Using a cutter, cut the pvc tubes of 12mm diameter into pieces of the following length: 2x28cm, 18cm and 35mm.

I glued it by following the picture attached.

To build a rack mechanism, cut 2 rectangles of cardboard 12x6mm, remove the upper layer to find the teeth. They are glued on end of the internal faces of the two tubes. Please see the picture below.

Step 6: Shaping Locking Wheel

I start by cutting the cardboard in 4 circles of diameter 30 mm. then, we will cut each of the 3 circles into 3 pieces: two half circles and a central rectangular piece of width 14mm. the semicircle pieces are glued superimposed as shown in the attached picture.

Step 7: Mounting

This step is used to mount the parts already built. We start by making two holes for rotation axes of the two locking wheels, always we can use a pencil for the perforation. After the installation of the two locking wheels, the tongues lock is placed in its position as shown in the attached picture. we can if we want to build a box that covers all the locking mechanism.

Step 8: Front of the Box Door

For each end of the three axes, we glue a circle with a diameter of 25mm. Then we glue two numbered wheels from 10 to 85 for example 35mm diameter using hot glue.
Finally, we glue the opening lever on the third axis. Regarding the lever, you can choose any shape that you like.

Step 9: Door Rotation Solution

For the fixing and building the system of rotation of the door, I use two pieces of wooden sticks and I enter them in the groove of the cardboard at a distance of 2 cm from the edge as figure in the picture attached.

Step 10: Building the Box

Finally, we cut the cardboard into 5 rectangles whose dimensions are as follows :

- 2 rectangle 30x34cm

- 2 rectangle 42x30cm

- 1 rectangle 42x34cm

After, we glue them using hot glue, always keeping the perpendicular angle between them.

Step 11: Watch

In order to not miss any details and to follow all the real chain of the instructable, enjoy to watch the video tutorial attached.
Hoping that you liked this creation !