This time capsule has a special mechanism that doesn't allow it to be opened unless the plunger is pushed in. The part that makes this a time capsule is the plunger can be locked with a tamper proof cable seal.
Here's the Fusion 360 file to see all the details. http://a360.co/1NR4fX3
Cable Seal http://www.mcmaster.com/#2083t52/=zo8thp
2" round aluminum rod
2" OD "1.878ID aluminum tube
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Step 1: CNC Turning
So long story short. These parts are hard to make. The gap between some of the parts are .001". Patience is required. Rushed parts just won't fit.
All the CAM setups are in the Fusion 360 file. There is/was a bug in Fusion 360 Turning/Milling for ID boring parts with one open end, so a lot of the CAM operations are workarounds to get around the bug.
Some secondary operations are needed if your CNC Lathe setup doesn't have a sub spindle. I used a Haas ST-10Y and a manual lathe to finish some of the parts.
Step 2: Assembly
Once you have all your parts, the assembly should be pretty straight forward.
The top and bottom pieces press fit into a 2"OD aluminum tube.
The plunger assembly involves .125"OD magnets to hold .25" precision steels balls in place.
All the screws are M2 screws.
And a light spring pushes the plunger back up.
Step 3: Put Stuff Inside
The tube can be cut to any length, so you can fit anything that fits into a 1.8" hole into this time capsule. It's aluminum, so it's not meant to be buried. It's more of a shelf piece or hand-it-down-to-the-next-generation piece.
The final piece is a cable seal to lock the plunger. Once you pull the cable through the seal, there's no going back without cutting the cable.