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This Instructable will walk you through the steps required to copy a key just like secret agents do in movies. This includes making the impression of the key and casting it in zinc metal. Note that while copying keys that you own is absolutely fine, copying somebody else's key without permission or with malicious intent is almost certainly an offense punishable by law.

I really enjoyed the process of creating this key copy, mostly because I was shocked to discover that it actually worked. What had started as an offhand, careless afternoon activity turned into a viable copy of my house key. Enough small talk - let's begin key smithing!

Step 1: Make the Molding Compound

As I said before, this project was not very planned. I was bored and wanted to make a copy of my key in one day, so I had to get creative in order to accomplish the whole process in one day. Thus, some of the steps listed here may be less than standard, but hey - they worked!

To copy the key, you will need an impressionable substance capable of withstanding the molten zinc at ~800°F. Plaster works well for this purpose, as shown in this video. However, plaster also has a bunch of water in it and takes quite a while to dry out completely. When pouring molten metal, you do not want water in your mold - it will create steam, bubbles, and possible explosions. So, in order to copy the key on one day, I had to figure something else out. My solution was very creative, to say the least. :)

I used dried-out carpenter's wood filler paste as the base material for my molding compound. It was the first good item that I saw around the house. If you replicate this project, you should mix around 3/4 cup of wood filler with a very small amount of water. Mix it well; it should be a soupy paste. Next, add some flour to your paste until it becomes thicker. Eventually, you should be able to remove it from your mixing container and then knead it like bread dough.

Note: This project is not gluten-free. :)

After you have kneaded your dough until it is soft and well-mixed, it should feel just like a good hunk of bread dough.

Would aluminum work as well?
<p>I honestly don't know. If you got your aluminum hot enough and poured quickly into your mold (a funnel-shaped depression might help), I would give it a good chance of success. You should try it!</p>
<p>My mother took a correspondence course on locksmithing in the 60's so as a child I was familiar with the ideas of getting the key right. Later, as a custodian at a high school, I was always irritated that the teachers would let certain kids walk around with the keys and trust them with them for hours. As a result, some little genius copied those keys and there was a set the kids themselves had. I was accused of not doing proper secutiry when I kept begging them to change the locks and not trust the kids with their keys. Yes, the kids got in several times. Once got a saw from the metal shop and then went in the office to try to saw the safe open. They set off the fire alarm making smoke doing so. There was never any money stored in the safe, the office staff just kept paperwork in there. If there had been money it would not have been much, very small, unsuccessful school. </p>
<p>I cant do it</p>
<p>I have used pewter for casting but it is way too soft!</p>
It's great you tried it! I would recommend melting some zinc pennies, because zinc is much harder (and stiffer) than pewter. Also, watch that the sneaky key doesn't break itself off in your lock. :)
<p>I do commend you on your self discipline, and the understanding that without failure it's difficult to understand the success.</p>
Thank you. It is quite nice to look back and see that repeating the failed procedure eventually led to such a rewarding success.
<p>Maybe a tip- The vents should go to the top. The vents and sprue should attach at flat parts you will have less difficulty cleaning up the pattern when you remove the casting from the mold.</p>
Hey thanks! That sounds like good advice for the next time I do this and for anybody replicating their own keys. Also, thank you for including the picture - it helps with visualization.
<p>Hello,</p><p>What kind of bottle of gas is that? Is it propane? mapp gas, etc. What would i look at lowes or walmart regarding that gas bottle?</p>
I used propane with a normal entry-level self-igniting torch head. MAPP gas would work just as well and could probably be used for other high-heat metal-melting projects (gold, etc). In a store, you should find the blowtorches in the plumbing or general tools section. Good luck!
Nice job. I would like to point out to all those critics out there (especially ac-dc) that this IS instructables where we are supposed to find new ways of doing things, and have a blast doing it! Though purchasing a key may be a better way to acquire a house key, this was obviously a hobby project and was a cheap and fun way of doing it.
Thank you! It was a very fun project, especially playing with a molding compound that I am nearly certain nobody has used before.
<p>Cheaper to go to lowes - no. Easier maybe. Reliable yes. It's a 30 mile drive one way.</p>
<p>It's your own fault if you choose to live so far from civilization that it takes 30 mi. drives just to get a key made anywhere.</p><p>Otherwise, time is money so yes rather than spending an hour or more doing this it would be cheaper to pay a buck to get one made and it'll last a lot longer, work a lot better in a less than perfectly clean/operational lock cylinder.</p><p>Spy angle aside, if you're supposed to have a copy of a key then have one made that's good for the life of the lock ahead of time.</p>
<p>Either way, I've got a half dozen key machines, but without the key to copy and a blank to cut it on to, casting is a lot faster!</p><p>There are plenty of keys out there that your local hardware store doesn't have, and even some your locksmith can't get hold of.</p><p>Good Instructable. Needless to say, there are &quot;secret squirrel&quot; versions of this available.</p>
<p>You can also experiment with Field's metal:</p><p><a href="https://en.wikipedia.org/wiki/Field%27s_metal" rel="nofollow">https://en.wikipedia.org/wiki/Field%27s_metal</a></p><p>More expensive than Wood's metal but less toxic.<br></p><p><br></p>
Well actually, I have experimented with Field's metal, and it is quite fun! I keep a blog, so you can read about what I did with it right here: http://sciencewithscreens.blogspot.com/2014/09/experiment-26-fields-metal.html. In a sort of funny coincidence, I contributed to the very Wikipedia page you referenced me to! Field's metal is also an awesome substitute for mercury.
<p>you can download &quot;CIA Field Expedient Key Casting Manual&quot; to see something similar. I would think with all the epoxy resins out there you could use some type of plastic you could use instead of metal? might only produce a key that could be used a few times though. </p>
Wow! I didn't know that even existed! I'll have to check it out. Also, you are right - although epoxy is strong for holding stuff together, I am nearly certain that zinc will be better for repeated use in a lock. Epoxy is probably good enough for a covert reconnaissance mission, though. :)
<p>Nice, especially the way you showed the failures. So often they aren't shown and when we have the same problem we are left clueless.</p>
<p>Nice job! Zinc may not be the hardest metal in the world, but it'd work great for an occasional backup. And considering brass is a common material, zinc is in the ballpark. It'd probably last longer if you make sure your lock is well-lubricated, too ;)</p><p>On a safety note, be careful with zinc. It's nowhere near as bad as lead, and most of the toxic effects of zinc are either temporary (&quot;metal fume fever&quot;) or due to ingested zinc (like dogs swallowing pennies). But, if you see a blue-white smoke coming off your molten zinc while casting it, go get some air. It's most dangerous during brass casting, because the melting point of brass isn't too far from the boiling point of zinc.</p>
Yeah, zinc can sometimes be a real pain to cast. It is so easy to overheat it in a charcoal fire and then it forms weird wispy stuff on top and, as you said, white smoke. The green flames that come off of overheated melted pennies are cool, though. :)
<p>When you clamped it, you may also have made things so airtight that the air trapped inside couldn't escape. When you mold lead toy soldiers, you should always dust the mold faces with talcum powder, which provides just enough gap for air to escape. The same might work for you, although the rubber bands seem to have done the trick!</p>
Oh, cool! I should try that sometime. Thanks for the explanation.
<p>Good ways to vent air from the die are either (1) scratch, but don't cut, tiny &quot;whisker vents&quot; away from the die cavity. They should be VERY fine. They will be small enough to let air out but not liquid metal. Or, (2) cut a small channel from the bottom of the cavity back up to the top of the die next to the sprue hole. This one can be wide enough to allow free flow of metal. When you see metal flow up to the the top of this hole, you know the cavity is full.</p>
Ahh, that is a good idea. Actually the second method is also used in greensand casting. I used that basic method for the sprue and riser system in my aluminum bowl casting: https://www.instructables.com/id/Cast-an-Aluminum-Bowl/
<p>The wheel weight was probably lead. It can be surprisingly hard to scratch when it isn't alloyed with something. The old wheel weights were always lead.</p>
Cool, thanks for the info. I should measure its density and compare that to the periodic table density for lead.
<p>Hello,</p><p>So to melt the metal, you put pennies in a can and pointed the lit torch at the pennies? How many minutes does it take to melt 10 pennies?</p>
Yep, pretty much! It doesn't take long to melt 10 pennies - certainly under 5 minutes, maybe even less than 2 minutes.
<p>Good</p>
<p>I enjoyed reading your instructable, it was very informative, with a nice touch of humor. </p>
Thank you! The process of writing the Instructable is nearly as fun as actually doing it!
<p>isnt it cheaper, easier and more reliable to go to lowes?</p>
Yes, but it isn't half as fun and it doesn't make me feel like a secret agent. :)
<p>Clever!!!</p>
Thanks! I like your diverse and interesting Instructables, by the way!
Thank you.
<p>I don't mean to sound like a prick, but isn't melting pennies against the law? I would suggest something like tin solder or solder that is acid or lead free.</p>
Actually, that topic has come up a few other times. Take a look at this website here: http://www.coinflation.com/is_it_illegal_to_melt_coins.html. While altering coins with fraudulent intent or melting them for profit is illegal, it is absolutely OK to melt them or otherwise alter them for things like art. The difference is that you aren't making a profit off the coins or trying to pass off a quarter as a dollar coin. Thanks for being concerned, though!
<p>Alright, thanks for the heads-up, would tin be a suitable metal though? Or would it be too bendy?</p>
<p>For the purposes of a key, tin might be fine, but yes, ideally you would use a stronger metal. Lead would be the worst for a key, though - VERY soft and toxic. However, I haven't tried a tin key, so it might work. The mold was pretty reusable, so you could totally try a different metal if you made a tin key and it was too soft.</p>
<p>Yeah, I know tin has a lower melting point than zinc, I just didn't know if that is related to the strength of the metal.</p>
Well done, Pops- Excellent! You had me at the edge of me seat! Not just informative but entertaining 'Structable, as well. <br>
<p>Thank you! I enjoy writing.</p>
Nice job! I would like to try this mold making technique to make small pieces of jewelry. It seems like it would work good for silver and copper as well. Thanks for the info. ?
Thank you! Also, if you are interested in making jewelry, check out my Instructable on lost wax casting here: https://www.instructables.com/id/Cast-a-Metal-Ring/. With lost wax casting, you can make a complicated piece of jewelry just the way you like it in easy-to-sculpt wax and then cast a replica in sliver, gold, or anything else.
<p>wow! thanks for including the attempts AND the success! awesome Instructable, great job and fun to read :) </p>

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