Introduction: Hollow Bolt Dead Drop

About: My full time job is being a husband and a father to my three children. My paying job is a mechanical engineer. Every once in a while I get a little time to work on a project. As long as I live to be 1,000 y…

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.


Spy Challenge

Finalist in the
Spy Challenge