There are millions of doors on homes and cars and other things that have locks, but how many lock patterns are there? They can’t all be as unique as snowflakes, right? Do they sort this out by creating a lot of different lock patterns, and making sure they don’t distribute cars/other lock sets in a manner that would make it likely that other people’s keys would open the locks? Or do they really only make one lock of a certain pattern and no more?
Pontiac Grand Prix’s (at least since the electronic remotes) only have 4 different keyless remotes.
I don’t know how many mechanical locks car manufacturer uses, but a friend of mine was in a rental car (Ford Explorer), unlocked it, got into it and was a half a mile up the road before he realized he was in the wrong car (same color both exterior and interior).
Cite? That seems absurdly low to me … These are only anti-theft-effective if there’s a pretty low probability of a random ‘key’ working on a random car.
Well, there are a number of things you can vary. The most obvious would be the number of tumblers in the lock, with each tumbler having maybe five or six different possible heights. You could then vary the distances between the tumblers, if you felt fancy. You can also add a whole extra row of tumblers, too, although I imagine such locks are expensive.
The house key on my key ring has five tumblers. If we assume that each tumbler is sensitive enough to allow a maximum of five possible tumbler positions, then we get a maximum of 3125 possible key combinations. If we assume 7 possible tumbler positions, then we get a maximum of 78,125 possible keys.
This is a purely mathematical analysis- someone who knows more about keys and locks could explain the hardware side of it a little better, I’m sure.
One thing also to consider is not all locks are as sensitive as they should be.
I’ve made keys that were off and still worked. By rights they were off enough by siting that they shouldn’t have worked, but with a little jiggle the locked opened.
So it’s possible after a lot of use or whatever reason the lock or key becomes worn down and will allow itself to be opened when it shouldn’t
Yale locks used to bill themselves as being the first company to mass manufacture items in non-identical forms. I’ve never known a Yale key that opened anything other than the lock it was intended to open.
Tumbler locks have millions of possible combinations. While in theory two could be alike, it’d be hard to find them.
This doesn’t count things like passkeys* or locks deliberately keyed alike. But locks for houses have been nonidentical for over a century.
It may be different for cars. I know that some construction vehicles are all keyed alike; there used to be a problem about people stealing Ford steam shovels because they all had one key (convenient if you owned several, but also for thieves). I’ve also heard stories of people driving off with the wrong car. It’s possible the auto manufacturers are cutting corners by sticking with just a handful of lock combinations.
*In Russia, they passkey down the streetsky.
Not even close. The typical “Arrow” type house key has, as noted above, five tumbler positions with each capable of 6 different pin lengths for a total of 15,575 combinations. Long odds for finding a duplicate, but far short of being identical.
There have always been overlapping keys for cars but with the advent of the the computer chipped key it is now possible to reduce that to zero as it relates to operating the vehicle. A chip could have billions of combinations available to it. I’m surprised that nobody has come out with a USB memory stick as an electronic key so that people could program their own cars. You could feed in your high school poem on cheese-wiz as a security code and still have enough room left over for 24 days of continuous music.
How do you manufacture something where every unit is different? If you picked two locks in series off of the same machine would they be different? Or do they build one lock for six months, then go to another pattern. Are industrial machinery precise enough to change between each and every lock (or 100 locks*)?
*Any factory worthy of the name will be producing hundreds of thousands of locks a day, I would think.
One complication I know of is that you can’t vary the depths of the cuts too abruptly, or you’ll get a weak piece of metal that breaks too easily. So you might, for instance, be able to have cut depths ranging from 1 to 6, but any two adjacent loci can only have a difference of 3.
Another complication is that not all locks use all of the tumblers that the key would allow for. For instance, you might have several rooms in a building such that each room needs its own key, but any of the room keys will open the door to the building. In some cases, you can even have a master key that’ll open the building and all of the rooms.
FWIW, and no cite, I have heard car manufacturers make ~1000 key sets. As noted already (and I have heard similar stories) it is possible to use your keys on a car that is not yours. Just have to try a bunch.
ETA: IIRC Mercedes had some “laser cut keys” that in some fashion were an extra security measure. I think they dropped them when people lost their keys and were told a replacement set would cost a few hundred dollars.
You’ve never watched How It’s Made, have you? Yes, the machinery is easily able to make consecutive unique locks. The series actually did tu7mbler locks, and basically the machinery randomly selects a set of tumbler pins, and then cuts a key suing the pinset as a template. The key is then sent along the production line with the lock so that they are packaged together.
Oh, I forgot to mention another situation that might be of interest to the OP: In high school, we were all issued combination padlocks for our lockers. But friends often told each other their combinations, and it quickly became apparent that many locks, though they had different numbers, had the same pattern. For instance, one student’s might be 17-21-30, and another student would have 23-27-36 (the first student’s combination +6). So you could make batches of 40 identical locks at a time and just put the dial on differently, and you’d end up with 40 different combinations, but they wouldn’t really be secure, since you could get someone’s combo by finding out what the last digit is (by looking at the lock after they’d opened it), and then guessing which of about 10 different patterns they had.
Anecdotal cite for car locks:
When I embarrassingly locked my keys in the trunk while talking my girlfriend out to eat, the locksmith that came had a key ring with about 100 different Ford trunk/door keys and tried a couple dozen until one worked. Car was an 80 something Mercury Grand Marquis, without that nifty number entry thing that would have saved me $50.
Considering that Ford used those same keys for decades (early 70’s to mid 90’s IME), I’d say that there are thousands of like keyed cars out there in the real world.
Maybe it’s just late at night and I’m overtired, but shouldn’t this be 7[sup]5[/sup] = 16 807 keys, rather than 5[sup]7[/sup] = 78 125?
I love modern technology. 
I’ve done the same. Well, not a Ford Explorer, but my make and model of car. And the two times it happened, I looked over and noticed that the crapload of stuff that is usually in my car wasn’t in the one I just opened. And then locked the door and found my actual car.
House or office keys.
Schlage and Baldwin locks with a “C” keyway.
5 pin lock each pin will have 10 sifferent lenghts from 0 to 9. That will get you a combination of 100,000. If the differance is 8 or 9 the key can not be cut. If the differance is 8 or greater when the key is cut the differance will be 7. As an example a key with the binning of 46901 when it is cut will end up being 46921.
Now if you go to a 6 pin lock, mostly on commercial locks, the starting number will be 1,000,000.
Now throw in other keyway and I believe Schlage has 9 keyway.
Now if you want to pay a littler more get a Schlage Primus lock. It has a registgered side bar on the key and lock. Schlage keeps track of where each key was used and will not sell a like key in the same area.
Keyless Entry can be brute forced in 3129 key presses. Don’t get too excited about “electronic keys” just yet.
Often the difference in the price of a lock isn’t in materials or construction, it’s how many duplicates were present in the total run of locks/tumblers. A high-end top-of-the-line run would only make as many locks as there are unique combinations for the design. A low-end run might make ten or hundreds of each combination.