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Make a working key from scrap metal by reverse engineering a lock

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Picture of Make a working key from scrap metal by reverse engineering a lock
Have you lost all of the keys for your lock and need to make a new key from scratch?  Does the locksmith lack a key blank that will fit your lock's keyway? Grab a metal file, some scrap sheet metal, and read on for a rough & tumble do-it-yourself key making guide!
I made mine at http://techshop.ws

Reverse engineering a key from a lock is not that difficult, providing the lock can be disassembled. In order to follow this instructable you will have to have access to the lock itself, which usually means the lock is not locked to begin with. If you're hoping to make a key for a container that is currently locked, you'll have to pick it open first, or research the key making method known as 'key impressioning'.
 
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Step 1: Disassemble the lock

Picture of Disassemble the lock
The filing cabinet lock I was working on had an external housing that needed to be opened before the lock itself could be accessed. It had a set-pin that needed to be drilled out. Drilling the pin slightly off-center with a bit smaller than the pin was enough to prevent it from spinning in place, but disintegrated the pin sufficiently that the housing could be opened without causing undue damage to the rest of the lock. This is not usually a necessary step for standard door locks.

Once the lock has been removed from its housing (door handle, drawer, whatever), there is usually a cover on the top of the lock that holds the pins and springs in place. This cover is often clipped in place and can be removed without damaging anything. In my case, the edges of the pin holes were uncovered, but crimped half-shut and needed to be widened with a drill in order to extract the pins. As you remove the pins, keep them in order front-to-back and keep track of the 'top' and 'bottom' pins. Each pin has a specific shape that allows it to interact with the spring, with the pin above/below it, and/or the key itself, depending on where it is sits in the pin-stack. A helpful tool for keeping things straight is a small piece of paper like a post-it note folded into an accordion shape so that each pin-stack can be laid in its own trough.

Removing the lock core from the sheath is usually a helpful step even if it isn't absolutely necessary. I recommend  removal if at all possible (but don't pull it out until you've removed the pins, or they'll shoot everywhere!) Sometimes the pins cannot be removed except by pulling the core. If this is the case, be careful to expose only one stack of pins at a time, or you'll have some sorting to do when all the pins cascade out of the lock.
_soapy_2 months ago
Nice job. Buff it on a wheel or use light sanding to smooth it out a bit, & wear should be low enough it'll be fine for years.

I'd also recommend you always change the pins around when doing this, because that way you have revoked the old keys, which could be anywhere (stolen! )

I'm a pro, but I've done this on non-fitting-but-quite-close blanks so that I have the right blank for a job, on occasion. Sometimes even a locksmith can't get the right blank! I've yet to have to make a cylinder key from scratch though. Lever locks, on the other hand...

One other tip: you can file down the pins rather than the blank. It's a bad idea as a locksmith, but for a one-off gig like this, you can get the key quite close then file the tops of the pins that are sticking up a little. Just make sure they are all either right or too long. You can't file them longer!

Finally, if you want to improve the security of the lock against picking, you can file the longest pin around the middle, into an I (capital i) bobbin or spool shape. This makes picking harder. Do a top & bottom pin pair, which will annoy anyone trying to bump it too.

Great !

thinkpadt308 months ago

I am so glad you did this 'ible! I have an old lockbox to which I just lost the last key, and it is used to secure my class III medicine. More than once, I have found medicine missing, so this is a God-send! Right now, I'm having to pick the lock each time to open AND close it, so this will be so much easier. Your 'ible is very clear, so I feel confident I will be able to make a key now. Thanks again.

golond (author)  thinkpadt308 months ago

I'm glad this will see some actual use! Picking the lock twice every time you need to get into the box sounds like it would be a real hassle, but you're probably getting pretty good at it, eh? Feel free to message me if you run into anything unexpected. Good luck!

pvizgaudis8 months ago
Love the writeup. but if you wanted to really make it easy, you can do just a couple of the pins only. That would really save effort and time. Again I Love the writeup on this.

This recommendation is very good, and I would add, just use one pin in the reassembly, then you don't even need to fit a key. The lock will push in and lock, appear secure, and can easily be picked with a bobby pin, and yet if you stick a key in the lock, might push the pin past the shear line, and keep it from unlocking.

Sounds like good information.
skylane8 months ago

Burglars...PAY ATTENTION!!

if they have enough time to carve a new key from scratch, then they deserve to steal your stuff. asside from the fact that if they can dissasemble the lock in the first place to make a key, they're already inside.

TinkernTom8 months ago

As a professional locksmith, I have a few pointers.

Where are the Pin Springs in your pictures, and reassembly instructions. The springs are used to push the pin stack down onto the key, and they make reassembly much more difficult.

Use brass stock, instead of steel so that your new key does not act like a saw cutting into the pins and lock body which are made of brass and white pot metal respectively. Besides being easier to work and impression. You can usually go to a local lockshop and buy the proper keyblank for your particular lock.

You can use this technique for fitting a key because the tolerances in this type of lock are very loose.

Assuming that security is not your main consideration with this file cab, just reassemble without the pins and springs, the lock can be locked by pushing in, and opened with a nail file or what ever, and yet it will appear secure. Security is usually a matter of appearances!

Otherwise a fun exercise I am sure for a few curious, and hopefully they end up appreciating the work that some of us do daily!

golond (author)  TinkernTom8 months ago

All great points. Thanks for sharing your experience!

I'll try to take some additional pictures and modify the instructions to more specifically include the springs. They're definitely pesky little things to get back in.

I hadn't considered the wearing effect that a harder metal would have on the pins. Definitely something to take into account if making a key that will get regular use.

raevans558 months ago

I can well understand the feeling of achievement in creating the key. But in my view, the amount of work involved isn't really justified, as it would make a lot more sense to just go out and buy a new lock, which'll obviously come with a set of keys.

golond (author)  raevans558 months ago

Necessity is the mother of invention. In this case, I needed to lock a filing cabinet containing sensitive information before turning over a property to house-sitters. I only had a few hours notice that I was leaving town. The local locksmiths were all closed for the day, the office supply stores did not sell replacement lock/key sets, and hardware stores did not have key blanks for the keyway. Making a key was my absolute last resort!

raevans55 golond8 months ago
That wasn't clear in the article. So in that case, VERY WELL DONE!!!!
SRQ Sid8 months ago

Great write-up and explanation of lock term and functions. I hope I never have to do this but its nice to know it can be done with hand tools. Thanks.

togaclad8 months ago

Great write up!

I've done this exact thing. I used a dremel to do the coarse cuts. Also I found the local hardware store would sell or even give me blanks as a starting point. On the other hand if you want a cool looking custom job, this is the way to go.

shizumadrive8 months ago

I like the look of that key. Maybe a bit too pointy for going in my pockets though. Makes me want to make my own key grinder.

golond (author)  shizumadrive8 months ago

Yeah, I leave this particular key in the lock all the time, so sharp and pointy was okay! I just replaced a noisy AC motor in my furnace, so maybe I'll use that to make a 'key cutter from scratch' instructable. ;)

That would work.

Cool make the key cutter project. That would make a good grinder.
jexter8 months ago

Very nice tutorial, thanks for posting this!

I don't know much about how locks work, but if the original key is lost and can't be replaced, can you put the pins in different positions than they were originally? The reason I ask is that if you could start with the shortest pin in the first position, and you ended up filing to much off of your key blank on your first try, you could switch to the next longest pin and still use the blank instead of having to start over. Do the same with the next position, until you get the hang of filing *carefully* ;-) Would that work?

golond (author)  jexter8 months ago

Hi Jexter,

I think your question is closely related to my footnote on step 7. As long as you don't need any existing keys to work after you finish making your new key, you can rearrange the pins of the lock however you like.

If you do move pins around, be sure to keep top and bottom pin pairs together. Sometimes the top pins have different heights so they inversely match the variation of heights of the corresponding pins, sometimes they don't. If you end up putting a tall top pin on top of a tall bottom pin the resulting pin stack might be too tall for the lock, and the key will jam when you try to put it in the reassembled lock. Similarly a short top pin paired with a short bottom pin won't properly interact with the spring on top of the pin stack, and the pins can get stuck up in the lock preventing it from opening even when the proper key is inserted.

I think you already understand what I'm going to say next, but I'll say it anyway just in case. ;) I didn't mean to start with small pins at the front of the lock and work your way to the back of the lock incrementally increasing the pin size, like a ramp or a hill. Part of the security of a lock comes from alternating tall and short bottom pins in order to make it more difficult to pick open. Reordering pins is ok, but keeping things looking 'random' is a good thing.

If you really mess up the cut for a pin and don't want to start over, you can just leave out that stack of pins, but sacrifice some of the security of the lock to do so.

Let me know how it goes!

shizumadrive8 months ago

Interesting. I've never been able to salvage a lock after I took it apart though.

Nice work, I`m gonna try that !!!

That is insane! Bravo :D

Todd Gehris8 months ago

Great instructable!