Introduction: The Evil Cache

Picture of The Evil Cache

My girlfriend and I have recently started geocaching and we both really enjoy it.  We've seen/been to some neat places that we otherwise would have just passed on the road or would have never visited unless we were hunting one of these things down.
We have also been stumped by more than a few of the more difficult ones known as "nano" caches.  these things are nothing but a tiny canister with a magnet and only enough space inside to hold a rolled up piece of paper to log your visit, and people get really clever when they hide them.  So I decided to try my hand at making one of these evil little things.....only more evil!

Step 1: Materials

Picture of Materials

This is a pretty cheap project to make, all you need are some hardware bits you may have lying about and some simple tools.  the most expensive material needed was the nano cache itself, cost about $10 at my local R.E.I.


-A bench vise
-A pneumatic cutoff wheel (and air compressor of course, or a hacksaw)
-Some J.B. Weld
-A 1/2" diameter by 2 1/2" hex bolt ( I chose 2 1/2" to give me some material to play with)
-A 1/2" Nut that fits on the bolt
-Two 5/16" internal diameter washers (these are the exact diameter of the nano cache)
-One 1/2" internal diameter washer (This will fit around the hex bolt)
-A small rare earth magnet (I scavenged this off one of my girlfriend's old name badges from her job)
-A metal file
-Toothpicks & something to mix the J.B. weld in

Step 2: Clamp It, Cut It, Grind It

Picture of Clamp It, Cut It, Grind It

Secure your bench vise to your work surface. Screw the bolt onto the nut and thread it down close to the head of the bolt, this will give you a more stable surface to put in the vise.

Next cut a piece of the end of the bolt.
I decided that 1 1/4" was long enough to make the geocache look passable, in the end i want this to look like a bolt that penetrates something metal.  I filed down the treads a little where I want to make the cut.

After the end piece is cut off you want to make the cut end as flat and even as possible. To hold it still while being filed I screwed it part way into the nut and screwed the rest of the bolt in the other side, after hand tightening it was secure enough to put back into the vise and begin filing.

Once the end is flat and even file down the threads a little where it reaches the edge.  I didn't want to have any sharp edges on the thread.  I tried to make it look as symmetrical to the other end of the piece as possible.

Step 3: Grind Down the Existing Cache

Picture of Grind Down the Existing Cache

Now you want to flatten the top of the nano cache with the file to make it suitable for attachment to the smaller piece of bolt.

Unscrew the larger half of the hex bolt from the nut and place the nano cache in the nut with the smaller end of bolt you just filed and secure it in the vise.  The magnet in the bottom of the cache should help keep it from moving.  Now file down the top til it is flat and the new surface is even with the edge where the dome ended.

Once this step is completed you can J.B. Weld the top of the cache to the flattened end of the bolt you just filed down.  To keep everything stable I put the cache inside the nut with one of the 5/16" washers at the bottom.  Mix equal parts of the J.B. Weld together and apply a small amount to the filed end of the cut bolt.  Be careful not to accidentally glue everything to the nut!
I affixed it to an altoids tin and left it on a shelf to dry.

While this dries you can go to work on the head of the bolt.

Step 4: Off With Its Head!

Picture of Off With Its Head!

Now You want to cut off the head of the Hex bolt.

First I measured the thickness of the 1/2" washer and the thickness of the magnet.  The washer being about 1/8" thick and the magnet about 3/32".  To make things easy I put the washer on the bolt and marked it roughly with a sharpie to know where to cut.  Affix it in your vise and grind away CAREFULLY.  You want to try & make your cut as square as you can.
Once the head is cut free you want to put the washer back on to see how much more metal needs removing.  You only need to grind off enough to make the magnet flush with the washer.  To expedite this I put it back in the vise and carefully ground a little away with my cutoff wheel.

After another dry fitting with the washer and the magnet only a small amount of metal needed filed away to make the surface of the bolt even and the magnet flush with the washer.  Again, try & make it as flat as you can.

Now you want to J.B. Weld the magnet to the head of the bolt.  This can be tricky because the magnet will attract the metal in the J.B. Weld causing it to "crawl" so only use enough to get the job done.  It doesn't take a lot.

Spread a thin layer of J.B. Weld onto the bolt and do your best to place the magnet dead center on the first try.  Using a clean tooth pick clean away any excess J.B. Weld that might "crawl" onto the top of the magnet.  Place high on a shelf to dry.

Step 5: Finishing Welds

Picture of Finishing Welds

After all parts up to this step have dried it is time to weld the rest.

Take both 5/16" washers and J.B. Weld them together, try not to have it ooze out the edges.  Then take the 1/2" nut and put enough J.B. Weld inside it to only go about 1/4 to 1/3 of the way into the nut & make sure the threads have enough J.B. Weld to fill them in.  be careful not to use too much or you might not be able to screw the geocache together/apart when its done.  Apply some J.B. Weld around the outside opening of the nut as well.

Take the assembled geocache with the welded bolt end and carefully push it through THE END OF THE NUT WITHOUT THE J.B. WELD!  This can be a bit messy so take your time.  If you are worried you might accidentally weld the top of the geocache to the bottom half then unscrew the top and push the bottom half through the nut with a dowel,  you can then clean out any excess J.B. Weld with a damp Q-tip.  

After the geocache is through add more J.B. Weld to the bottom of the nut if needed and place the washers on the end of the geocache.  Wipe away any excess J.B. Weld with a wet paper towel and affix the whole assembly magnet side down on something magnetic (like an altoids tin) to dry.  You can also use a clean tooth pick to clear away any oozing J.B. Weld from where the nut mates with the washers.

Now to finish the head of the bolt.

With the magnet welded in place it will be easier to weld the washer to the head.  Put a small bead of J.B. Weld around the inside circumference of the 1/2" washer, try to only put it on the flat side and not the inside edge.  Remember the magnet will attract it.

Secure the head of the hex bolt in the vise with the magnet facing up.  Hold the washer securely with both hands (J.B. Weld facing down of course) and carefully place the washer onto the head of the bolt, you don't want the magnet to grab the washer it will be messy.  Place somewhere to dry.

Step 6: Final Shots and Placement

Picture of Final Shots and Placement

Now that everything is dry and securely welded make sure you can unscrew the threaded bolt end from the rest of the nut assembly.  If you were careful you shouldn't have to worry too much. 

Place the log inside, re attach the top of the geocache and find something outside that has a lot of nuts and bolts holding it together (like a water pipe assembly in a park or a metal gate).
Separate the two halves of the geocache and arrange them as if it were actually a bolt penetrating something metal.

Log the coordinates on a geocaching website and watch as the "didn't find it" responses grow and grow.

Behold the EVIL!


Jon B3 (author)2010-04-25

I hate "evil caches"!

But to help find them I always keep a "day-glo" vest and a clipboard in the cache-mobile. Put on the vest and despite glowing like an radioactive orange you can look over a structure for hours and no-one even notices you. You just look like a municipal or council worker. (And 'cause you're not actually claiming to be one no-one can hassle you for impersonating one)

Jot a couple of "notes" on the clipboard ever now and then, consult the GPS and you're set!

WPee (author)Jon B32010-04-26

REMEMBER don't walk TOO FAST or everyone will know you are NOT a government employee...
("worker" does not apply here ...use employee when talking about government types)

daxxvondrachen (author)WPee2014-10-06

I think the proper term is "placeholder" or "skinwaster"

qualia (author)WPee2012-05-12

i have alot of animosity towards my memories of the year i spent as a council employee. you wouldnt be that enthusiastic about working either if your job was picking up litter (mostly fast food wrappers and illegally dumped household garbage on a daily basis, garbage that you had to tear open and search through in case there were old letters indicating the identity of the culprit so they could be prosercuted.)

am seriously considering making one of these geocaches. i have a cnc mill and lathe.

and i still have the council worker uniform.

and plumbing overalls.

this could work.

could make heaps of these so they outnumber the actual load bearing bolts on a bridge and install them so overenthusiastic geocachers cause a serious disaster.


Pat_Maroney (author)Jon B32010-04-26

I like that idea, very clever.
Where does one get a day glo vest?

Jon B3 (author)Pat_Maroney2010-04-26

Around here most shops like KMart have them. But specialty work-wear and safety equipment shops should have them if your local big chain shops don't.

The basic ones only cost US$5 here because classed as safety gear and just about everyone who does a manual type job is required to wear one. Gardeners, mail-people, delivery people, cyclists, builders etc etc.

KJ4ZVQ (author)Jon B32011-06-29

if you have a local Tractor Supply Co., they will have them.

sparrowmict (author)Jon B32010-04-26

fantastic anti muggle disguise.   never would have thought of it 

Pat_Maroney (author)2010-12-07

Ok, Finally got around to placing this thing.
The Cache's name is "Asymmetrical"
coordinates are: N38 39.953 W121 31.212
Placed in Natomas CA
Happy hunting :)

GenAap (author)Pat_Maroney2013-06-13

I got on Google maps and did a 360 spin to look around. "This isn't to bad" I thought "A wall, some bushes, not much that can hold a screw" I thought.
Then I saw a metal sculpture,
Then a bridge,
Then a bunch of electrical boxes, a pipe coming out of the ground, a road sign, and a light pole.

If I'm ever in that part of California I'll try my luck!

the-police (author)2012-05-14

You should put it on a grain bin... that would be so evil.... there are 2000+ bolts sticking out on most grain bins... ;)

VagsmaCutter (author)2011-05-30

Make one that looks like a piece of excrement; a bird dropping stuck on a tree or an owl pellet. Something that would take guts to attempt to pick up with a bare hand. One time I cut my hand on the lip of a cache. It was kind of anticlimactic. I was tempted to sign my name in blood but decided against it. I later died of tetanus. JK about the tetanus but the rest is true. That was truly an evil cache. And, it was by a cemetery too. Aroooooo...scary! Nice work on yours.

Gelfling6 (author)VagsmaCutter2011-09-25

I think I must've made the entire forest of animals think I lost my marbles once, when I actually found a stage of a multi-cache, when I sat-down, and saw a blob of what looked like animal droppings, until I touched it with a walking pole, and heard a metal (pole) versus stone click. They do make them, usually with a cryo-tube underneath. I've actually found a few of these 'Nut & Bolt' containers here in Connecticut. they're not that hard to make, but I imagine a bear & a half to drill-out the end to hide the cache in. Another alternative, I've seen people put a Neodymium magnet in the nut, sea it in with epoxy, then insert the bolt with the log book into the rest of the nut.

Roflolommo (author)VagsmaCutter2011-09-25

better idea. stick of dynamite with a piece of rolled up paper inside. And have it rigged to explode at a moment notice.

jplate1 (author)2011-05-30

Woah! you violated Rule #1 of Geo-Caching.. DON'T TELL *MUGGLES!!!
( non-geo-cachers )

BigDrig (author)2011-05-29

Awesome! its great to know there are other Geocachers here.

Pat_Maroney (author)2011-05-29

Front Page again! Thank you to the powers that be at Instructables Im flattered to be chosen again.

A major snag I've run into with this cache: it seems the JB Weld likes to rust in the outdoor elements and therefore snap off of the top of the internal nano cache, a simple solution is to throw away the top of said nano cache and just screw the cut & filed piece of bolt into the nut.
If you really wanted to be clever and fashion some sort or rubber grommet you could cut a circular section of rubber from a flat bike inner tube and glue it to the bottom of the top bolt piece to protect the log.

Pat_Maroney (author)2011-03-23

thanks for all the sweet comments.
Unfortunately the top half of the cache got lost right after i placed it.
now I have to make a new one from scratch to replace it :P

rhm3 (author)2011-03-21

I've done a few Geocaches and am a memeber of If I were to come across this cache I would definiately leave it for the experts. LOL !

mash4077 (author)2011-03-06

this structible got me into Geocaching thanks!

DELETED_jorgegunn (author)2011-01-05

I havent tried any nanos yet made or found. We just made our first Geo cache. (its here on instructables) but this is so cool. I'm gonna try my hand at finding some but this will def be the first one i make. so wonderfully Wicked

Gottwinkies (author)2010-11-01

LOL! I like your kind of evil! When I first saw this I wasn't thinking geocache...and I find I am still wondering what else I can use this little container of evil for...Mouhahahhhaaaa

abun1991 (author)2010-09-17

I've always wanted to try goecaching, but apparently a gang called "the presidents" steals all the caches around where I live. *sigh*

krapphace (author)2010-07-28


axmon (author)2010-06-18

you are true evil and sicken me too the core. nah cheers bro il try thaton my friends who are keen on geocashing.

Rainh2o (author)2010-04-25

Or you can hollow the bolt out like I did, then you can put the log in a piece of straw inside...

mossimo3 (author)Rainh2o2010-06-16

Was it a hardened bolt? I hope not because you could wreck quite a few bits with that! I'm liking the aged look, it would definitely help it blend in

Pat_Maroney (author)Rainh2o2010-04-26

That IS awesome!

sparrowmict (author)Rainh2o2010-04-26

thats just wrong.... i love it

Rainh2o (author)Rainh2o2010-04-25

Then when you hide it you can thread it through an object with a hole in it.  I have made some more pretty evil ones in my day, if you want to see, contact me and I'll send you pictures of others

Dr.Bill (author)2010-05-23

And Why exactly would you want to hide a note so completely?
I did not catch that part.

Pat_Maroney (author)Dr.Bill2010-05-26

because its geocaching
thats kind of the point

peaceamidst (author)2010-04-20

...I don't understand what this is. Anyone care to explain?

jsgraham (author)peaceamidst2010-04-20

Geocaching is a high tech scavenger hunt involving GPS. Players of the game will hide a container, ranging from the size of a peanut to the size of a military foot locker. Yes, there is a geocaching container in New Orleans that is a huge trunk with lots of cool stuff in it to trade out.  Anyway, players will hide a cache, and then post the GPS coordinates on Other players will go find the cache. 

Once you get started in caching, you will find that it's addictive.  You get to see parts of the country or your own city that you would have otherwise passed by.  Some of my best friends were made while geocaching.  Best of all, it's family friendly.  In fact, we encourage families to get involved.

It's an environmentally conscious activity where we encourage those participating to clean up the planet as they are out caching. The geocaching website has planned events where all we do is get together and clean up an area or parts of the city. The activities are called C.I.T.O.; Cache In Trash Out. We like to leave areas better than when we arrived.... kinda like the Boy Scouts.

I encourage everyone to get involved in Geocaching. I can't think of a single negative thing to say about it, because it's so much fun.  And who doesn't like to go on a treasure hunt? It takes you back to those times on innocent childhood when you're in your backyard playing Pirate.

peaceamidst (author)jsgraham2010-04-20

Neat. What do you need to get started. Or more like is it expensive?

Wesley666 (author)peaceamidst2010-04-20

Really you just need a computer, you obviously have one, access to the internet so you can make a Geocache account, and Google maps, but Google maps makes it harder.  The true way of Geocaching is with a GPS.  They start at about $100 and go up to around $800.  Mine was $650 and is accurate to about 5m.

peaceamidst (author)Wesley6662010-04-20

    Aren't their gps apps for an ipod touch? If so do you think it would work for this, cause I have an ipod touch 2nd gen. Other wise I would go with google maps I guess. How do I start tracking them? Do I use that Geo aching site or something?

Wesley666 (author)peaceamidst2010-04-20

They do work for that.  They work not too bad.  I find an actual GPS to be better, it might be my preference though.  And yes, you use the Geocache website.  You go on, make an account and find a cache near you, enter the long. and lat. coordinates into the device (You connect it to computer via USB or something and you can write it directly to the device)  and then follow it to the coordinates.  When you are close, its all about a sharp.

peaceamidst (author)Wesley6662010-04-20

So do you think if I got a gps app could I just search it up and leave it as a stale page? Or does it not use the net?

jsgraham (author)peaceamidst2010-04-21

I've used the iPod Touch with the Geocaching app, and it will allow you to save the pages for offline use.  Which is useful when you're driving down an old farm road and no WiFi anywhere.

It's a very cool app, with lots of capabilities.  Some of which are useless unless you have an iPhone.  But I make do with what I have.  A true Maker will find ways of improving what they have without going out and buying the newest gadget to replace it.  We want to make said gadget.  Which is the reason for this site. ;-)

I'll agree with Wesley666 in that a true GPS unit is the only way to go.  Most smart phones use cell tower triangulation to pinpoint your location.  It's accurate to within 100 to 3500 feet.  Depending on building, terrain, electrical disturbances in the area, weather and much more.  Anyone who uses a smart phone to geocache with success is a very lucky person.  The accuracy is, in a word, crap.

You can find Garmin and Magellan GPS receivers on eBay at affordable prices.  If you get one for say $70.00, you're doing pretty good.  And all the pretty screens and other bells are whistles are not necessary to geocache.

We had a couple of kids in our area that wasn't even using GPS to find geocaches.  They would print out the satellite image from the site, and go to that location and just hunt for the cache.  They found about 25 caches this way.

There's more than one way to do things. Improvise, Overcome, and Adapt.  It's not just words that the Marines utter. Get out there and have some fun. :-)

Sabata (author)jsgraham2010-04-28

Just to add to what jsgraham wrote above, Amazon and Wally World currently sell the Garmin eTrex H (the yellow, no bells or whistles model) for <$80. It's perfectly serviceable for newbie and veteran geocachers. Their accuracy is surprisingly good and I know several people who use them.

Besides eBay, don't forget to check Craig's List and the for sale section at the forum for good deals. When people get serious about geocahing they often buy a newer, more complex unit and sell their old (basic) unit at a good price. Many also seem to be willing to give an even better deal to newbies on a budget in order to help get more folks involved in the sport.

Entropy512 (author)peaceamidst2010-04-20

Not sure, but I think only the iPhone has a GPS receiver, not the iPod Touch.

peaceamidst (author)Entropy5122010-04-20

    Okay, I might look into it. Anyway I found one on the site close to me, might have to check it out sometime. Less then a mile.

Zinventor (author)peaceamidst2010-04-20

 Correct me if i am wrong, but i believe that the iPhone only has a network-based location system. My dad has a 3gs, and it cannot find location if there is no reception on the cell, where my Motorola Droid, witch has a real GPS chip works great, no matter where i am. There is also a way 

Revolverkiller (author)Zinventor2010-04-20

that is true if you  rely on the google maps app which loads the map data via network. but if you use Navigon or TomTom which has the maps already loaded on the phone, you can use it with no network (like mine because im not on AT&T anymore) so yeah there is a real GPS chip in the iphone, but use something other than google and you can go anywhere regardless of signal

Elfin (author)Revolverkiller2010-04-21

My kids and I just started geocaching.   I have an old iPhone that doesn't have a GPS.   We use the free Geocaching Intro app (called "geocaching intro" and published by Groundspeak) and if we're within cell range it works to find the rough location (within half a mile) of caches, but it's nowhere near accurate enough to actually find the cache.

My husband has a 3G iPhone, and we use the same app to actually find the caches.   So far, we've stayed within cell range, and it's pretty much walked us straight to the cache.   

The paid version of the app is $9.99, which seems a little steep to me.   My only other complaint is that if you leave the interactive map open it seems to burn through battery time very quickly.

jsgraham (author)Elfin2010-04-21

Elfin, I promise you that if you pay $9.99 for the full version of the app, you will not be disappointed.  I've been caching for nearly 5 years, and I did not hesitate to pay $9.99 for the app.  Other Windows based applications for geocaching will cost you at least $25.00. And you have to drag your laptop with you when you cache.... which BTW I've done.  A netbook is much easier.

But even so, what ever gadget you want to use to geocache will probably need a GPS attachment to work. 

Kudos BTW on actually getting the iPhone 3GS to actually lead you to a geocache. I'm impressed.  Even the 3GS doesn't have a GPS chip in it, so you're relying on cell tower triagulation.  There must have been a good cell tower saturation in your area or something. 

Paladin (author)jsgraham2010-04-22

 Not true at all. The 3 and the 3GS have a GPS device. Use them all the time. 

For all you doubters:

jsgraham (author)Paladin2010-04-23

Then I stand corrected. My apologies.

FWIW, a GPS chipset will only be as accurate as the government allows.  You can make a chipset that is accurate down to the nearest nanometer, but there are restrictions on civilian accuracy to somewhere around 5 meters.  I don't care what the device tells you, it's wrong.

Case in point, My Garmin Summit HC, which is supposed to have a high sensitivity antenna in it, showed accuracy down to 3- feet all the time.  There were many times I stood at the coordinates of a geocache, and the unit was off by more than 15- feet (about 5-meters).

Entropy512 (author)jsgraham2010-04-23

That is false.  There are no restrictions on how accurate a manufacturer may make a civilian GPS receiver.  This is why there are highend survey GPS receivers that do various signal processing tricks (carrier phase tracking, advanced differential GPS, long-period averaging, cross correlation of the encrypted signals on each frequency to obtain ionospheric delay info from the second frequency without actually decrypting the signal, etc.) to achieve millimeter accuracy.

However, the following ARE true:
The government has the technical capability to degrade the unencrypted civilian signal (C/A signal) intentionally (called Selective Availability) and in fact did so globally until approximately 2000.  SA is now only enabled in specific regions when deemed necessary.  (Interesting thing - back when SA was globally enabled, it was actually DISABLED during the first Gulf War because there weren't enough P-capable military receivers to go around, so servicemen were purchasing civilian units.)

There is a second signal, the P signal, which is encrypted and can provide more accuracy than the C/A code without any fancy tricks - sales of these units are highly restricted, and control of the crypto keys is even more restrictive.

Most of the tricks above are computationally expensive and/or require the receiver to be stationary for long periods of time, so you don't see that kind of accuracy from most civilian receivers.  (Actually, Garmin has a new waypoint averaging function in some of their receivers that adopts many of these tricks.)

As far as displayed accuracy - If a receiver displays anything other than DOP numbers (which have a specific definition derived from satellite geometry), it's a contrived measurement arbitrary to the manufacturer.

Also keep in mind that your unit may have been dead-on with its coordinate display, but the person who placed the cache may not have had a good signal/good satellite constellation/good receiver.

Starting in a few years, civilians will get access to a second signal, the L2C signal, allowing for dual-frequency civilian receivers without any fancy tricks.

About This Instructable




Bio: I'm a total geek when it comes to tools and craft supplies. Never let me in a hardware or craft store without a leash ... More »
More by Pat_Maroney:How A Prosthetic Leg Is Made!Embroidered Page From The "Slender" Game!A Bright Idea With Origami Stars
Add instructable to: