Mechanical Cardboard Hand

In this project we will be building a mechanical cardboard hand, that will we be able to flex its fingers and grab objects.

• Gather the following supplies.
• 1 Piece of cardboard that is 30cm by 12cm.
• 1 Piece of cardboard that is 17cm by 12cm
• 4 Pieces of cardboard that are 14cm by 3cm
• 1 or 2 straws
• Scissors
• String
• Hot glue gun and some extra sticks.
• A ruler will be helpful

The first step is to glue the four 14cm by 3cm pieces of cardboard onto the biggest piece. These will be the four fingers of the mechanical hand. It is possible to make five fingers, you'll just have to adjust the size of the pieces so that five fingers fit instead of just four.

Next, using a ruler or just your hands, fold the fingers to add joints just like a real finger has. The ruler is helpful to line up all the folds across multiple fingers, and the straight edge will also help make sure that you have straight folds. These folds are the spots where the fingers will bend later. I did 3 folds on the normal fingers, and only did 2 folds on the "thumb". This way the line up closer to real fingers.

The straw will act as guides for the string that well add later. First you'll need to cut the straw into smaller sections. I cut my pieces to about 1cm each, although I did not measure each individual cut. Using the hot glue add one piece of straw to each digit on the fingers. You can also add straw in the "palm" section of the hand. It's not necessary and I didn't do it in my example, but it can help guide the string as well.

Run a piece of string through all the straws on the first finger, and then tie it off. I went ahead and used a dot of hot glue on the knot just to help hold it in place. I also left a lot of extra string after each finger. This will make a later step easier, so it's a good idea to do it if possible.

Take the last piece of cardboard, and using the ruler again to help with the folds, make it into a triangular shape. I actually messed up when making mine and glued it on after folding it. It actually would have been better to cut the hand holds out first before gluing it. Either way, once it's cut and attached your hand should be able to fit through the opening.

To tie the string off, I closed my finger first, and pulled the string pretty tight. This way I could gauge how tight I needed the string to be, and adjust it if necessary. I like to set it so that my finger being completely closed will pull the string tight enough to close the finger as well. Tying the strings into loops for your finger to fit through can be a little difficult, and a few of my loops didn't turn out exactly like I wanted them to by the time I was done. After you get all the loops tied though you should be ready to put your hand through the handle and test it out.