Making Keys After The Apocalypse

Making keys is an amazing art with a lot of skill and technique involved. For those of you living in a post-apocalyptic world, [Dan] has a much simpler solution to the problems of having one too few keys for your locks and deadbolts – just cast them out of scrap with the power of the sun.

To make the mold of the key, [Dan] is using a two-piece plaster of paris mold. First, a thick layer of plaster is laid down in a small container and the key floated on the surface. After drying, sprues are put in with clay and the key embedded in a curing plaster block. After a few hours, a proper mold is created ready to receive molten metal.

The casting material is zinc – not as hard as the original steel key, but more than strong enough to turn a lock. This zinc is melted in a steel and plaster crucible with a gigantic fresnel lens.

As for the utility of this method of copying keys after the apocalypse, we’ll have to wonder how practical this method is. A giant fresnel lens isn’t just something you randomly find unless you’re going house to house looking for projection TVs, and finding a can of mold release after the end of the world is beyond credulity. That said, it’s a cool demonstration of metal casting that can be easily accomplished at home or at any hackerspace.


50 thoughts on “Making Keys After The Apocalypse

    1. Most 3D printers that print using metal particles are extremely expensive (i.e. $100,000+), so I don’t think so. A lathe is only a few hundred dollars, making it cheaper than many 3D printers, since it doesn’t require a 3D scanner, and can actually work with metal.
      Note: You could use plastic 3D resin printing and then a tension wrench to turn the key. Of course, after the apocalypse keys won’t matter much.

          1. You have it backwards. With a lathe, the material you are working spins, and the bit is fixed. With a mill, the material is fixed and the bit spins. So Lyon is right, and PCF11 needs to get his facts straight.

    1. It is. There is no challenge and very little skill needed if you already have a copy of the key. Alternatively a profile cut from a credit card works reasonably enough. Just don’t put the turning torque on it.

      I can’t think of any normal keys that are steel. Steel destroys the soft material inside locks. Nearly all keys are brass or nickel-silver, most chromed out or nickel plated. Some keys are iron or aluminum. An average person can go a lifetime without seeing a key made of any particularly hard material. He is on the right track with zinc though. Most cheap or cheapish locks have a great deal of cast components made of zamak, a zinc based alloy. It casts well, machines well, is strong enough, and very inexpensive. It may even be easier to simply melt down old rim cylinders and use that material than buying zinc to use.

      1. That is just plain and straight out wrong! Locks of any quality (meaning they carry a rating grade 1, 2, or 3) and also most that are listed by UL or under the National Fire code.
        Locks, are made of very detailed and ultra precision parts and close tolerances, a correctly assembled cylinder that is free of damage and grime exerts little force on the key, if the cylinder is worn or dirty and just a bit more load exerted on the key it becomes impossible to get the key out of the lock! a Brass key may be fine for a 4 pin padlock or your gym locker, but locks in commercial applications are a whole world away (hospitals, fire stations, apartment complexes, retail stores, schools) in these places a brass key wouldn’t last a month! the pins in a cylinder (the part that touches the key are made of case hardened steel, cylinder plugs can be a alloy of brass or zinc, (not a soft type but one made for machines). In fact some key blanks are STAINLESS steel, (Schlage locks lettered keyways (C, G, H, J, K , L) Where there are 3 levels of keyway a L Blank fits all the others, this makes for a very thin blade on this blank as it must clear the wards in all the other keyways below it, if it were made of just steel it would bend and warp very quickly, this blank (originals from Schlage) are stainless, don’t know about 3rd party venders products) If an unsuspecting lock smith tries to use a punch type cutter on one its likely he will shatter the cutters carbide jaws! If care and proper cooling is not used when using a wheel type key machine or he feeds it to fast the blade will warp and possibly crack!

    2. Casting a simple object isn’t efficient, but for complex geometry that would required a lot of machining, it’s still the best way to go. I think the article should focus more on the fact that you can concentrate an interesting amount of energy out of the sun with relatively affordable lo-tech optic.

  1. “A giant fresnel lens isn’t just something you randomly find unless you’re going house to house looking for projection TVs” — uh, yeah, that is one of the first things I would be doing post-apocalyspe, once the first few layers of Maslow’s pyramid were sated. Because having a reliable source of high-temperature power that does not need fuel is a good thing.

    Using plaster as a mold means you do not need a final mold-release — just break the plaster off. Plaster is recyclable with a baking step, and, well, see above re: giant fresnel lens. For form removal, any surface lubricant will do, so all that automotive grease sitting around everywhere is a good target.

      1. If I remember correctly, plaster of paris is often used in fire resistant containers. Basically it is just gypsum+water. When heated it releases the bonded water as steam and decomposes into either gypsum or something else depending on how much moisture content is left. Doesn’t really matter anyway as adding little moisture will turn that something else back into gypsum anyway, then it is back into plaster of paris land.

      1. I know euro pennies are steel with a thin top/bottom layer, and I expect that’s the same everywhere.
        But the coinage doesn’t mater be they pennies or dimes or whatever, you can melt coins just not alter them then pass them out again as coins in the US I hear.

    1. I think come the apocalypse there’s gonna be a lot of scrapped computers, and demand for distributor heads and spark-gaps.

      My friend once didn’t have the right parts to fix the fuel injection on his Land Rover. So he took off and replaced the manifold (I think!) and spliced a carburettor into the air intake! To me, that’s amazing! Prior to that he’d spent time doing engineering on ships, so I suppose he wouldn’t be afraid of big chunks of heavy metal. He gave the job up in the end cos it’s hard to meet women in the middle of the ocean.

      1. Just to point it out in case it isn’t obvious, since this isn’t really something I know a lot about… my point is he converted a fuel-injected engine into a carburetted one! The fuel injectors came right out! Maybe it was the cylinder head instead of the manifold that they were attached to. Or as well as.

        1. Most got the point you where making. Any engine that spent it’s life in the past sucking on a carburetor can do so if the fuel injection equipment is replaced wit the carburetor equipment. The question may be how well it will run with valve timing optimized for fuel injection. Any hardcore prepper is already using vehicles, with a stock pile of replacement parts.

          1. AIUI the carburettor was a completely new addition. Like I said, he just spliced one into the air intake. Surely fuel-injected engines don’t have carbs, so no such engine would ever have used one in the past? Who knows what sort of spare stuff he had in his garage? Our journey was delayed a bit when the engine broke on his way to my house, so he had to go back and replace a jubilee clip. Something to do with the radiator I think.

            I spent most of our 200 mile journey asking endless technical questions. It’s nice when someone really knows their stuff, and is at least partly self-taught.

  2. Plaster of paris will make very high accuracy molds, though shrinkage might make this a challenging way to duplicate a key. It is used for prototyping die castings by the lost wax method. The mold needs to be baked at ~250 F for 24 hours before casting. Otherwise you risk a steam explosion and molten metal flying around which is seriously dangerous.

    zinc alloy die castings (e.g. automobile door handles, etc) are a much better source of metal than pennies. As noted, beware of zinc fumes. The traditional treatment for zinc poisoning is drinking lots of milk.

    Mold release is easy. Can you say PAM? But anything that will keep the pattern from sticking to the plaster will do. After the metal is cast the mold is destroyed, so “mold release” is only required for the pattern.

    Plaster of paris can be reused if you dehydrate it and grind it up. It’s just dehydrated gypsum (i.e. calcium sulfate). A container with a bunch of marbles and a means to rotate it will do the grinding.


    Even trace amounts of lead will cause the casting to disintegrate over time. This is the cause of castings that just crumble to dust. At one time, it was common practice to use a bit of lead in the crucible to speed up melting of the zinc alloy. The disintegration is caused by intergranular corrosion.

    There are zinc alloys which are very nearly as strong as steel, so it’s not to be sneezed at. It’s much easier to cast even than aluminum.

      1. The curse of far more than just toy collectors :-(

        I’d seen it many times, but didn’t learn the cause until I got seriously interested in metal casting. It was a great mystery for quite a while. I think the scanning electron microscope was what settled the matter.

        FWIW The real key to survival is knowing how things work and how to fix them when they break. Guns are useful at times. But knowledge is far more valuable. When I melted a hole in the #3 piston of my Karmann Ghia, I pulled out the #3 pushrods and drove home (~100 miles) on 3 cylinders at 45 mph. I still think that’s one of my best hacks. Drove it for almost a month like that while I waited for a new engine to arrive.

  3. The Universal Post Apocalypse Key is generally known as a 4 pound sledgehammer. Light enough to carry around while harvesting resources, heavy enough to open closed entrances blocking access to said resources.

    The only problem with a Universal Post Apocalypse Key is it’s rather difficult to re-close entrances it has been used to open, so not the ideal tool for opening a place you may wish to use to live in or for storing resources you’ve harvested.

      1. Checking out all the comments from your IP, here’s what everyone is missing. Wait, they’re not actually missing it, because my liberal moderation policies let it through. Still, I wanted to point out the inanity of your comments. Anyway:

        > you really are a dingus.

        > hahahahahah

        On a The Hackaday Prize post, for context:
        > so did anyone win this pile of junk yet?

  4. Or you can spend a little time learning how to pick locks… with some basic tools that can be found scattered all over the streets and sidewalks (broken bristles from street-sweepers) and a little bit of practice, you’ll never need to worry about keys after the Apocalypse… (and unlike smashing locks with a sledgehammer, you can RE-LOCK a picked lock)

  5. Dan does have videos of experiments that may have utility and had others that could best characterized I’m doing this because I can. I’d file this in the latter folder. I thinks is time for another episode of Denise cooking with solar power while wearing her bikini.

  6. Anybody familiar with Bronze Clay? It’s an offshoot of Mitsubishi Materials Precious Metal Clay use it in whatever mold you have it goes in a wet stiff paste & put it in charcoal powder in a stainless steel vessel put it in a kiln for the proper time & you should be good to go!

  7. Can’t see much need for keys or locks in an apocalyptic situation. You can’t be tied to one spot. The fortress is just setting yourself up for the eventual siege. Small groups of armed moving individuals seems like a better idea to me. Eat what you kill rabbits squirrels, dogs, cats, cows, horses, pigs, snakes, lizards, what ever will produce the calories. You need a way to purify water and make a fire. Most of all ammunition.

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