How are all locks/keys different when mass produced?

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Recently moved to a gym that uses padlocks for locking your stuff, they sell them too for an inflated price of 3.5$, jokingly I tried my key on a friend’s lock, and one more random one, of course it didn’t work and it made me curious.

My question is how do factories make all keys/locks different even at these cheap mass produced kinds that are probably sold for 0.5-2$, how is it worth for a factory to “use different patterns” at that price, or how do they do it?

In: Engineering

37 Answers

Anonymous 0 Comments

They use different combinations of pins inside the lock that match up with the grooves on the key. Each lock has a unique combination of pins, making it so only the right key will work.

Anonymous 0 Comments

They aren’t. There’s lots of standard keys that are used in thousands of different places. Even seemingly random ones only have a limited number of permutations so if you bought 100 locks and keys you’d find some that were the same.

Anonymous 0 Comments

Well they’re not all unique one key will work for a lot of that make of lock . If you’re using a $2 lock security isn’t really that important

Anonymous 0 Comments

They aren’t.

When MasterLock makes a new padlock, there are only maybe 200 different keys for that padlock that they make. Enough that it makes it unlikely someone would just so happen to have the same key as you, but it’s not impossible.

Same thing goes for car keys too, tho with the advent of more digital cars that makes it more complex.

But back when those keys were nothing other than a remote control, it was possible to find another car of your make and model that you could unlock with your key.

Anonymous 0 Comments

They’re not all different. I once walked up to my car, unlocked it and sat down before realizing it wasn’t MY car, just an identical make/model that somehow worked with my key.

This was before keyless entry. I have to imagine that those can be much more unique than a physical key.

Anonymous 0 Comments

For the lock side, they have a handful of pins of different lengths, and you change which length you put in which location. Cutting the keys is relatively easy to automate, as there’s a defined depth of cut for each location.

It’s also possible they make hundreds or thousands of locks with the same key, then switch to a different key each shift, mixing locks from different production runs when they ship them out.

There are also factories that always use the same key, for example CH751.

Anonymous 0 Comments

I had a buddy in college who walked out to the student parking lot, unlock and get in a red Honda, put the key in and drove off. He almost made it out of the lot before he noticed it was definitely not his car.

Anonymous 0 Comments

Sometimes they have a remarkably small set of unique keys or combinations. Three personal stories in order of scariness (**one with nuclear war implications**)

When I was in high school, I went to the right locker in the wrong bank of lockers (i.e. not my actual school locker) and my combination opened the locker. When I saw the contents didn’t match what I expected, I closed it and got out of there, just in case someone would think I was trying to get into someone else’s locker. I’m not sure if it was a coincidence it worked, or if every bank of lockers had the same pattern of combinations.

I do know that most inexpensive combination locks have enough “slop” that there are not really that many unique combinations.

When I was stationed in upstate NY in the early 80’s, I went to the wrong car in the mall parking lot and used my key on a car that looked like mine. I was able to unlock the car and only when i got in did I realized this wasn’t my car. I don’t recall the model, but the car was a GM.

Again, while stationed in upstate NY (Griffiss AFB), a co-worker discovered that his dormitory room key was the master key for our work-center and the next door Command Post (i.e. the people who would relay message for the B-52s to go and kill 40 million people). When his key was inserted in the command post lock, the entire cylinder would come out and a screw driver could be inserted and unlock the door. We were supposed to be “buzzed” in, but he was able to walk in and nobody noticed.

I was able to convince him to “accidentally” discover this on our work-shop and turn the key in. Had a bad guy had that key, he could have taken over the command post and prevented the flying of B-52’s if a war order had come in.

**tl;dr school lockers, car locks, and key to nuclear command post issues.**

Anonymous 0 Comments

there’s literally a thing where if you see some one getting a lock, chances are the ones on the shelf with it are keyed identically so you could just buy one of them and let yourself into their house later. there’s a code on the box that tells you exactly what key it uses even.

Anonymous 0 Comments

They aren’t. Even Car keys aren’t unique. Back in the day, I had 2 friends who both owned a Geo Metra. One day friend A left my house and realized 10 minutes later that he was driving friend B’s car. Both of their cars had the same jey for the ignition but oddly their keys didn’t work for the other car’s doors.