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
This is one of those “picture is worth a thousand words” situations, so [here you go](https://commons.wikimedia.org/wiki/File:Pin_tumbler_with_key.svg).
In pin-and-tumbler locks, the key works by moving the pins so you have a straight line between red and purple pins that lines up with the line between the yellow and green cylinders. Until you get that all lined up, the pins are in the way and stop the yellow piece from rotating.
That explanation out of the way: The yellow and green bits are easily mass produced. The springs are easily mass produced. The purple and red pins are mass produced in a variety of sizes. The part that varies between locks is just choosing a random-ish assortment of pins, and cutting the key to match the pins, and even that is fairly simple to mass produce.
While you can’t have infinite variations of pin setups, you do have several thousand different keys for the same lock type, so randomly stumbling into an identical key is fairly unlikely.
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