This is my second version of a dead drop spike. It is based off of several designs I saw in a book on spy gadgets. They would have been used for passing stolen documents and film between an agent and their handler, storing money and documents as well as other tasks. More practically it would work quite well as a geocache.
The advantages of this design are:
1) The lid locks in place. The previous version is only a friction fit which means that you have to have a pair of pliers if you want to remove the body.
2) There is an o-ring to seal the lid.
3) The lid and spindle are detached allowing it to be removed if you want to place a USB drive or some other object inside.
I have also lengthened the side wall by 1/2" and shortened the shank of the point by 1/8".
Cost for materials: ~$20 Canadian. (I had some of the materials and scrounged the rest. It might cost more if you have to buy a longer section of pipe.)
• Pipe cutter (optional)
• Lathe with cross slide
• 1/8" dremel bit
• 1/16" dremel bit
• 17/64" drill bit
• 1/8" drill bit
• 1/4" bit (I used 3/16")
• 1/4" milling bit (optional)
• Small file
• 1/8" diameter rod
• Glue applicator
• Mixing dish if using 2 part epoxy
• 1" long section of 3/4" aluminum rod.
• 1 1/2" long section of 3/4" aluminum or plastic rod.
• 3/4" external diameter, 4" long section of aluminum pipe
• Two 1/4" long sections of 1/8" diameter stainless steel, steel or aluminum rod
• O-ring that is as close to 3/8" internal and 5/8" external diameter as you can find. You will likely have to get a mixed bag with a couple of spares
• 1/2" long section of 1/4" stainless steel, steel or aluminum rod
• 9" long section of 1/16" diameter wire
• glue intended for use with metal
• About a foot of strong string.
Step 1: The Side Wall
Cut the 3/4 inch diameter pipe to length (4 inches). Round off any burr that is formed. At one end of the pipe cut two pairs of 1/4 inch long guide lines on opposite sides with the hacksaw and then open them up with the 1/8 inch dremel bit.
You can either mark and cut the grooves for the locking lugs now or wait until the top has been made, but not assembled, and use it as a guide for the 1/8 inch dremel bit.
This is the side wall.
Step 2: The Point
Take the 1 1/2'' long section of the 3/4'' rod. Using the lathe, turn a 3/8'' long section down from an exterior diameter of 3/4'' to 5/8''. The internal diameter of the pipe may not be exact so use the side wall to check that it fits snugly onto the pipe every now and then as you turn the piece down.
Turn a point on the opposite end from the one you just turned down.
This is the point.
Step 3: The Lid
Take the 1'' long section of 3/4'' rod and turn a 1/2'' section down to 5/8''. As with the point, use the side wall to check that the diameters actually fit.
Turn a 1/8'' wide groove 1/16'' away from the 5/8'' diameter end.
The exact depth of this groove will depend on the o-ring that you have to work with. I used a drill index and found the largest size of bit that I could fit the o-ring around, but still comfortably slide the bit and o-ring into the side wall. I then reduced the diameter of the groove to that size. You will have to test the fit before moving on.
Drill a 1/2'' deep, 17/64'' diameter hole in the 5/8'' diameter end.
This is for the spindle knob to fit into.
Remove from the lathe. Drill a 1/8'' hole through the rod, centered 5/16'' from the 5/8'' diameter end.
These are for the lugs to be glued into.
At this point you can either:
1) drill a 3/16'' hole centered 1/4'' from the 3/4'' end, and then mill a 1/4'' deep flat surface 3/8'' from the end on both sides of the 3/4'' diameter end,
2) You can drill a 3/16'' hole through the 3/4'' diameter end, centered 1/4'' from the end and counter sink it.
If you have a knurling tool I would suggest going with the second option and then knurl the surface.
Step 4: The Spindle
Take the 1/2'' long section of 1/4'' rod and cut 1/16'' deep grooves along its length with the
hacksaw. With the dremel and the 1/16'' bit, widen both grooves.
This is the spindle knob.
Bend the 1/16'' wire over the 1/8'' diameter rod as close to the middle as possible. Trim the ends so
that the overall length is 3 1/2''.
This is the spindle wire.
Step 5: Dry Fit and Gluing
Dry fit all parts together as show above. If they fit together properly then glue them together following
the instructions for your glue. Once the glue has set, slip the o-ring into its groove and tie on the
Step 6: Some Variations
I am not completely certain that the notches which the locking lugs fit into would withstand frequent or
more careless use.
This could be solved by either adding two extra sets of lugs and notches or by increasing the width of the
locking part of the notch by 1/8'' to around 1/4'.
Step 7: Youâre Done
There are a few ways that you can wind paper onto the spindle. The spindle has space for a strip of paper up to 2 3/4'' long or two strips of 35mm film. The way I have set it up is to make a small notebook out of water-resistant paper. I think it would be slightly easier on the notebook if you thread it onto the spindle just past the staple however if you are using it for geocaching and it will be handled by people who are unfamiliar with the spike, I would suggest threading the notebook to its middle as it is less likely for the notebook to slip off when you are opening and closing the spike.