So a teenager having our Dutch fall-holiday wanted to make something. We decided on a Cryptex.
The Cryptex is a prop from the movie "The Da Vinci Code" where they have to decode the Cryptex to open it. It is suggested that the Cryptex is a design from Leonardo Da Vinci, but I can't find any proof of that in a very very thick book I have about Leonardo Da Vinci.
I think we did very nicely so here is our try on this already well documented subject.
To open the Cryptex and get to its contents, you need to turn a couple of rings with letters on it to form a word.

The most important (and hardest) preparation for this project is getting four pipes that fit inside each other. Luckily I have bought an old crashed hang glider some time ago and the leading edge of this glider has already three of the four pipes we need. (please don't shoot hang gliders out of the sky for this project)
We started the build without knowing what our fourth pipe would be, but we where sure that we would find something.

Step 1: You Will Need...

Materials:

4 pipes that fit inside each other
Some small bolts (for me M3)
Some +/- 10 mm aluminum material (round bar in the with of your biggest pipe would be even better)
Xerox sticker material
Epoxy glue

Tools:

Metal saw (Gang saw works great)
Jig saw
Drill
Ruler
Pencil
Screw driver
Laser printer (or copier)
File
C-clamp
Thread tapper
Lathe

Step 2: Choosing Your Dimensions

How many letters
To decide how big the Cryptex will be, we first have to decide how many letters we want to use. (We both made a Cryptex with seven letters. I have no idea how many letters the Cryptex in the movie has)

The width of the letters
Next decision is the width of the rings with the letters on them. It must be wide enough to grab and turn but small enough to be compact and look good. We choose 15 mm.

The space in between the letters
Our design has spacing rings in between the letter rings. They must be the width of the head of the small bolds you are going to use. (I made mine just a little to small so I had to alter my original design. The kid did his just fine)
With our original design this should be +/- 5 mm.

The width of the endings
On both endings there will be an extra ring. I think that it would look nice when this ring is a little longer than the letter rings. I decided on making that 20 mm. The kid had other ideas.

The total length
My Cryptex should be something like 175 mm long.
7 Letters x 15 mm + 6 in between rings x 5 mm + 2 end rings x 20 mm
7 x 15 + 6 x 5 + 2 x 20
105 + 30 + 40
(mine will be a little bit shorter because I made the in between rings to small)

Step 3: Sawing the First Pipe

To make this Instructable a little bit easier, I will name the different pipes:

Pipe 1 - the inner pipe that will contain the content of the Cryptex
Pipe 2 - the second pipe is in my case the smallest of het hang glider pipes
Pipe 3 - the center hang glider pipe that will be the inside of the letter rings and spacer rings
Pipe 4 - the biggest pipe and the outside of the letter rings and spacer rings

These names will refer to the base materials and not the finished rings and pipes.

Sawing the first pipe to length
We take a piece of Pipe 2 and saw it a bit longer than the 175 mm we need. (We cut it a little to long because we can always cut it shorter, but never make it longer.)
- Later on the inner tube containing the secret content will go inside this pipe and the turning rings will go around it. -

Making the slot
This tube needs a slot where the pins from het inner pipe will go trough. We will make the the pins from the M3 bolts so the slot needs the width of the head of the bolts. (5 mm in my case)
To keep a bit of strength in the pipe we will not cut the slot al the way to the end, but stop just before.

Where we want to end the the slot, we drill a (5 mm) hole in the pipe. (mine had already holes in it)
Draw two lines from the side to the drilled hole.
Saw the lines with a jig saw. (be sure that your saw blade is short enough that it can't hit the underside of the pipe.
File the slot smooth.

Step 4: Making the Letter Rings

Clamp a piece of pipe 3 to a piece of pipe 4 with a C-clamp
Saw of 15 mm pieces (for me 7 times)
Take the ring made from pipe 3 outside the bigger ring
Mark 5 mm (the size of the M3 bolt heads) on the smaller rings
Saw a gap of 5 mm out of the smaller rings

Step 5: Making the Spacer Rings

Do the same steps as with the letter rings. (only now 5 mm wide)
You will need one less spacer than you need letter rings.
In my case 6 spacers for 7 letter rings.

Step 6: Bottom and Top Rings

To finish the outer part of the Cryptex, we just need to make the bottom and the top ring.

We saw this ring again out of tube 3 and 4.
For my design I used two 20 mm rings. (the kid used 14 mm)
Again we need to cut a slot in the inner ring. (for the bottom ring the slot doesn't need to be al the way trough)

Step 7: Cut to Length

Now al the outer rings are finished, we can measure the exact length the Cryptex will be.

Put all the outer rings on the tube we made from pipe 2.
Mark the part of the tube that is longer than the stack of the outer rings.
Saw the part that was sticking out of.

Step 8: The Inner Capsule

We found an old shock absorber that fits exactly inside the pipes we had.

First we had to saw it the right length. Just 10 mm shorter than pipe 2.
Because the shock absorbers where really old, we had to clean and sand them.
Measure the distance of the spacer rings exactly.
Drill 2.5 mm holes (for M3 bolts)
Thread the holes with a thread tapper
Screw the M3 bolts in the holes (I had to do it from the inside out because I made my spacers to small)

Step 9: All the Parts

Here a picture off all the parts until now.

On the top:

bottom outer ring
bottom inner ring
outer letter ring
inner letter ring
outer spacer ring
inner spacer ring
.... this four several times
last outer letter ring
last inner letter ring
top outer ring
top inner ring

On the bottom:

the tube with the slot in it
the inner capsule with the pins on it

Step 10: The End Caps

It took us a long time to decide on the end caps. We decided on milling them from aluminum on the lathe. I didn't have any round bar in the right size so we used 10 mm thick aluminum plate.

Cut from the plate a square just bigger than pipe 4
Cut the corners from the square
Put the plate 5 mm in the lathe
Mill the 5 mm sticking out down to the size that just fits inside the inner capsule (do this very carefully and slowly)
Turn the plate around (it will fit easy now)
Mill the remaining plate down to the outer dimension of the outer ring

Do the same for the other platen only this time mill the first half until it just fits inside pipe 2.

Step 11: Glueing the Rings

Now we can glue the inner rings inside the outer rings with 2 component epoxy glue.
It is easy to take off the excessive glue with some warm water and soap.
(be careful not to get your gloves stuck between the rings when you slide them onto each other)

The spacer rings are finished now.

Step 12: The Letters

The letters we printed on a transparent adhesive printable sheet. To calculate the size of the individual letters I used this formula:

Ø * 3.14 / 27

where:

Ø = the diameter of the outside of the letter rings
3.14 = Pi
27 = the amount of letters we want to put on it.

Before I printed on the adhesive sheet I first tried on a normal piece of paper. Some printers are not very accurate with the dimensions of the prints they make.
I cut out one row from the test sheet and checked the size.
Only now I printed the letters on an adhesive sheet and cut the strips out. (I printed some extra because I had room left on the sheet and you never know)

Now it is time to decide what word to use to open the Cryptex.

Stick the adhesive strips on the letter rings with the letter for the word that opens the Cryptex above the gap in the inner ring.
Our result is really nice.

The letter rings are finished.

Step 13: Put It All Together

Now it is time to glue it all together. This might well be the hardest part of this project. (at least for us)

First put the cap on the tube that was made from pipe 2 (we didn't need glue here, just a rubber hammer)
Glue the end ring on with the slot over the slot in the tube (be sure to remove excessive glue with warm water and soap)
Put the first letter on (this ring doesn't need to be glued)
Now glue on the spacer ring. This is the hard part. When you use to much glue you will get your letter ring stuck. When you use to little your spacer ring won't be fixed. I used a little gop of glue, put the gap in the spacer ring over it and than turn it in place, so the gap in the spacer is over the gap in the tube. This worked almost perfect.
Repeat for the other letter and spacer rings.
Finnish it of with glueing on the last ring.
Let it all dry for a couple of hours.

Separate from the outside we can put the end cap on the inside capsule. (again we just needed a hammer but you might need to glue this)
Make sure you put the end cap on the right side of the pipe and put it on strait.

Now it is just waiting for the glue to dry.

Step 14: Finishing

Make sure that you mark the gaps in the spacer rings BEFORE you put the inner capsule in the Cryptex for the first time!!!

I marked the gaps by drilling small dents in the rings.

FINISHED!!!