Introduction: Hollow Bolt Dead Drop

Picture of Hollow Bolt Dead Drop

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.



Everyday_Machinist (author)2015-06-29

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.

Bban (author)2015-03-15

Great build

roberto111 (author)2012-06-02

that is nuts

eklam (author)2012-05-06

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.

bioboy725 (author)eklam2012-05-29

I immediately thought about that too.

nomooremr.niceguy (author)eklam2012-05-06

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

hankjr5 (author)2012-05-07

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

poofrabbit (author)2012-04-24

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

jeanluc83 (author)poofrabbit2012-04-25

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.

Goodhart (author)jeanluc832012-05-01

Hmm, I have neither a lathe nor a drill press....I will have to think about this.....

jeanluc83 (author)Goodhart2012-05-04

There are lots of different ways the same thing can be accomplished. Just be creative and use what you have on hand.

Exocetid (author)Goodhart2012-05-03

Need neither.

Get a piece of metal tubing with a thick wall.

Thread the tubing with a thread cutting die (quite cheap at HF).

Close one end of the tube--epoxy paste would work fine. Paint with metal colored paint to match tube.

Get a short bolt that will fit in the tube open end. Wrap bolt with rubber bands, press fit into end of tube.


(variations abound)

Goodhart (author)Exocetid2012-05-03

Hmmm, yes that gives me a LOT of ideas....thanks.

nomooremr.niceguy (author)2012-05-04

It may be that I'm just ignorant, but I'm only wondering, would it be feasible to clamp your bolt into the lathe and while turning it on the lathe, simply apply pressure with your hacksaw? Or would it be better to do it the conventional way? Just a thought. I've not worked much with lathes, but as a college student, I have access to them on campus (I'm an E.E. with several M.E. friends. They get me on the lathes whenever I ask.). One last inquiry, Would anyone know how to reverse tap the inside of the bolt? Would it be practical? Might it improve performance? Just thoughts. I appreciate your input, advice, answers and time. Have a great day!


I wouldn’t recommend trying to use a hacksaw while the lathe is running. I’ve tried it and never had much luck. It is too easy to bend or break a blade. If you get a good quality blade it will only take a few strokes to get through the bolt.

Using left hand threads would not be all that much harder but a left hand tap and die set would be quite a bit more expensive.

4freds (author)2012-05-04

Evil geocache idea!!!!

Zargon (author)2012-05-03

NO... you WRITE messages. Isn't that RIGHT?!

Ludwig Von Mech (author)2012-05-03

Brilliant. Good Show.

Prsnltrnr (author)2012-05-03

This is a great tool for Geocaching! People make these all the time for it. You can even buy them at an expense. Keep up the great work!

JettaKnight (author)2012-05-03

I found a bolt in the parking lot the other day. I should go check if the head is removable...

rashoot (author)2012-05-03

Reminds me of someone using it to hide some crack. I saw on a tv show

jimmy lobotomy (author)2012-05-03

Just like Rudolf Abel! (Famous Russian spy based in New York)

MFXPYRO (author)2012-05-03

For a little more security you could left hand thread the head, this also means that if someone was undoing the bolt the head wouldn't come off and give the game away

jet engine 16 (author)2012-05-03

well being cheap i managed to use a piece of 2x4 that had a hole in it that i drilled to fit the bolt and all i did was i put the bolt in the hole and put the piece of 2x4 in my vice (not forgetting to cut off the top) the i took my drill and made the hole in the bolt, after that i simply used a file to resize the the top that i cut off and i was done! :) the only problem with this is i used a piece of double sided tape on the top of the bolt so the top didn't slip out of the shank it still looks like a bolt but one the adhesive where's out the top slips out of the shank...

zevidg (author)2012-05-03

Nice for a fire steel :)

tristantech (author)2012-05-01

That's pretty neat. I did something similar once in school where I passed messages to friends by stuffing notes into hollowed out Crayola markers. When markers dry out, instead of tossing them, you can peel off the cap on top, pull out the ink sponge (it's not very messy) and replace it with a spy message of your choosing. You have to find a marker that doesn't have a cap that's molded on -It has to be easily removable.

KontaKt (author)2012-04-26

So you right messages on the paper and hide it in the bolt? Cool!

About This Instructable



Bio: 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 ... More »
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