Hollow Bolt Dead Drop





Introduction: Hollow Bolt Dead Drop

Spy Challenge

Finalist in the
Spy Challenge

I made this dead drop a while back just to see if I could.  I didn’t even know that was the name for one of these things until I came across the Spy Challenge so I thought it would make a good entry.

It is made from a 1/4” bolt.  It can't hold anything much bigger than a postage stamp.  The general design could easily be used with a larger bolt.  A 5/8” bolt would be a good size for urban geocaching or would be about the right size to conceal a micro SD card.  An O-ring could be added to the design to make it water tight.

A lathe is required for this project but it is a good chance to practice some basic skills.  Total cost for materials was less than a dollar (I think actually free) and it took about an hour to make.  Unfortunately I didn’t take any pictures when I was building it so I’ll do my best to describe how it was built.

I used a 1/4” bolt about 2" long but any bolt or even a large spike or nail will do.  An old used bolt would be good if you wanted it to blend in with its surroundings.

Clamp the bolt in the 3 jaw chuck with the head sticking out about 3/4”.  Using a hack saw cut the head off the bolt leaving about a 1/2” of the shank on the head.  This could be done with a parting tool but a hack saw was faster for me.

Face the end of the piece remaining in the lathe.  Leaving the corner sharp will make it looks more seamless when assembled.  With a #25 drill, drill a hole about 1 1/4" deep down the center of the bolt to form the cavity.  The hole is then taped #10-24 to a depth of about 3/8”.  It is important that the threaded hole is square to the face or the head will not sit square.  De-burr and remove from lathe.

The head is then clamped in the 3 jaw with the shank sticking out.  Turn down the shank to 0.15” by about 1/4" long.  Small cuts are required since it is only being held by the head.  A small grove is added just below the head to ensure that it seats fully when assembled.  The shank is then threaded using the lathe.  The threads were then chased with a die.

Everything is then cleaned up and assembled.  The finished bolt can hold a piece of paper about 1" square.




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    should have made the thread on the shank left handed so if someone tried to randomly unscrew the bolt from wherever it is, the head wouldn't come off revealing the stash spot

    Thanks for the comment. It's nice to see there are still people looking at this.

    You could certainly use left hand threads. I didn't have a left hand tap to use on this one. For a larger size you could probably thread it in the lathe using a small boring bar. I have never made a left hand thread so it might be a fun project in its self.


    Great build

    The thread should be done such that it unscrews if you turn the head clockwise. This is what the soviets did in the cold war, since most people would assume that it would unscrew normally, and try turning it anti-clockwise.

    I immediately thought about that too.

    Precisely why I asked about the reverse tap! (Though I doubted anyone else would know about that history)

    sounds like a lot of work to hide a little of nothing,...

    I think this is a great entry! This is a pretty brilliant idea!!

    Thanks but I can't claim credit for the idea. In fact there is another version that can be build without a lathe found here.