I made a Cryptex

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Garden Shed Projects

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Hi all. I have something I would like to share with the group. I don’t get a lot of time in the work shop and have to snatch an hour here and there. As such I tend to build small things that offer me a bit of a challenge. I have recently taken an interest in puzzle box’s so decided to build the most secure type of puzzle box. A Cryptex.

I feel it qualifies as the most secure due to the number of possible combinations. Mine will have 6 tumblers with a full alphabet of 26 letters on each. My calculations put the total number of possible combinations at slightly over 300 million. 26 to the power 6.

Not really too complicated but I have come up against a few challenges along the way. I initially wanted to make both the inner and outer bodies in timber but couldn’t fathom a way to do this with the kit I have so decided on some 50mm stainless tube for the inner and 50mm copper pipe for the outer. The outer needs to be cut along it’s length and opened up so it fits over the stainless pipe this will also provide a channel to house the pins.

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I wanted to see face grain when you look at the wheels which meant laminating the available timber together. I have some beech which I have reclaimed. These are then sliced in to 15mm thick squares which will form the tumblers. I have a small pillar drill however I didn’t appreciate how much power would be required to drill a 56mm hole into end grain beech. I tried a Forster bit which was a non starter as the drill couldn’t turn it I also tried an adjustable spade bit and had the same issue. I ultimately settled on a metal hole saw which didn’t remove too much material at a time allowing the drill to cope.

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I made a couple of jigs up to hold the peices steady while drilling. I then tidied both the inner hole and outer edge with the spindle sander.

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Each of the rings requires a rebate to the inside which will allow them to rotate around the pins and will ultimately provide the lock. This groove was put in using the trim router on a board.

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Now I have the tumblers formed I want them to appear uniform so as not to give any indication of the unlocked position. I run a length of all thread through the body including the end caps and all 6 tumblers. Put a nut and washer on either end and put the lot in the drill press.

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Using a sanding block I rotated the assembly to remove any high spots. This took far too long so I fired up the belt sander. With the rotation of the drill and belt sander I quickly had a fairly uniform barrel. I don’t have a photo as it was definitely a 2 handed operation. At this point I numbered the barrels as their position is now fixed.

The tumblers were round but even with only 1/2mm to 1mm play it still looked a bit untidy so I decided I would chamfer the edges of the rings so the slack would be less noticeable. With the router fixed in the vice and a 45 deg guided bit I took off a chamfer of approximately 2mm from all the edges.

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Not sure if it is because of the end grain but I couldn’t stop the router bit from burning the wood and it also left a bit of a raggedy edge. This was quickly dealt with by the spindle sander.

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That pretty much completes the main barrel of the piece.

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So I now have the barrel formed and I need to start thinking about how I am going to stop the tumblers falling off of the outer body. I make up a smaller and thinner ring using a similar technique which will be fixed to the end of the outer body.
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I initially thought about sticking it on to the end and housing it into the end cap. However I decided this would look unsightly when the thing is open and housing it into the last barrel would look better.
The rebate was cut using a 25mm guided cutter in the trim router. The small inner ring fits snugly inside the outer. The inner ring was then fixed on to the end of the outer body with epoxy and clamped, I am hoping this will provide some stability to the outer body as the cut up the middle has caused it to flex a bit. This ended up being tricky as the epoxy continually failed and I ended up using CA glue which seems to be better.
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As an aside for future versions this may be a solution to make the combination changeable by doing this on each barrel, for now this one will have a fixed combination.
While this is drying I have cut a strip of beach at 10mm wide by 4mm deep and put a slight curve on the top to match the inner curve of the barrels as this will be notched to form the pins of the lock and be stuck to the inner body with epoxy.
I drill a series of holes along the line where the lever will sit to act as a key.
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I could definitely have drilled these holes in a straighter line but they will be covered by the beech so hopefully no one will ever know. I run a file up the line to take off any burrs and also to give a bit of a key and then epoxied and clamped in place.
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Next up is the cutting of the notches in the tumblers which will fix their position ultimately defining the location of the finished combination once the letters are fixed.

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Once these are all cut the final length of the copper outer sleeve can be determined and cut. I have fixed a disk in the end using epoxy which I have attached to the end ring using 5 screws, temporary fixed with 2 screws in photo, which can be accessed through the pipe and will allow me to remove the barrels in future should I need to for any reason.

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I have fixed the other end ring to the inner body in the same way.
 
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I now have the main barrel fully formed apart from forming the pins which will allow them to turn. I will leave this task untill I have the letters sorted.
So to the letters. I have ummm’d and arrr’d about the best way to achieve this and have decided that anything free hand is a non starter as looking at my handwriting you’d be forgiven for thinking I am a GP.
So I print and laminate? I think this would look cheap and not be robust. Individual letter decals? Would need a lot of focus to align properly and there would also be a risk of them coming off.
I have decided to get 7mm beads with the letters stamped onto them and my plan is to drill a 7 mm hole and fix an individual bead into each hole.
A jig will be required to ensure that the holes are aligned. I dissect the circumference of a circle into 26 by working backwards using pie. 10mm x 26 = 260mm divided by 3.14 = 82.8 making my radius at 41.5mm.
I cut out a circle to this size a cut a notch in at each mark.
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Using a bit of plastic sheet to locate the positions I knocked up a jig. The idea being to drill 1 row of holes then click around to the next slot and drill the next 6 holes 26 times.
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I then drilled a series of holes in a piece of timber to act as guides when drilling and attached to the jig.
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The drilling of the holes for the beads was pretty monotonous but quite rewarding. The jig worked fairly well but proved that any inaccuracies in the marking out of the gauge wheel would be translated into the final piece. I have decided the slight inaccuracies give it a hand made look but it is some thing I need to work on. Just to note I also drilled a hole on each end cap at the point the combination is to be read an then taped them up straight after drilling to avoid any careless mistakes later
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Before I start the job of fixing the beads I have given all the components a coat of Danish oil. Initially so all the tricky, hard to reach areas are covered but also any spilled or surplus glue will be easier to wipe off.
The fixing of the beads was a job I wasn’t looking forward to but it needed to be done. The beads are 7mm with a hole through the middle as they are intended to be threaded onto string. The hole proved useful as it provided a handy aid to align and square the letters using a useful installation device fashioned from a paper clip.
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Getting them to sit flat and true in the hole proved challenging but the occasional light use of the universal persuader sorted them out. A total of 158 beads including the 2 markers for the combination took me 2 hours of intense concentration. As usual these tasks are never as difficult as you think once you get started. All the letters are now fixed. They were stuck in using Gorilla super glue micro precise. Good stuff. I ended up having to remove the first one I installed as it sat too high and it took some getting out I can tell you.
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All components are now complete so I gave them a good coating of Danish oil to finish. I have also buffed it up with some bees wax.

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I have made a couple of discs in what I think is sapelle to cover the holes caused by the hole saw in the early stages.

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It works reasonably well and I have till Christmas to fettle it so may rotate the barrels daily to see if it beds in. Currently the 3rd and 4th barrels are a bit tight but I am reluctant to loosen any further incase it naturally becomes looser over time.

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Typically for me it is a little rough around the edges and there are a few things I would do differently. Mainly the letters didn’t quite turn out as expected.
That being said I am really happy with the outcome and feel like it’s another step along my woodworking path.
 
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