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How do Combination Locks Work?

combination lock ScottDaleCombination locks are everywhere; we use them on our lockers while we’re in school and we use them in our adult lives as well from locking up our bikes to locking up garages. For something that’s quite small and ubiquitous, it’s always surprising to learn just how effective and strong they are. Here’s what makes them the safety powerhouse that they are.

Inside a combination lock (the kind of lock with a curved bar and round body with a numbered dial on it), there are three “cams” – rotating or sliding pieces used to transform rotary motion into linear motion or vice-versa. One of the cams will be made of metal and will be directly attached to the dial of the lock. The other two cams are usually made of plastic and there will usually be two spacers that are specially made to fit between the plastic cams.

The cams will be fitted onto a molded shaft on the lock’s back and the stack of cams will be pressed together by a spring once the lock is put together. It’s this spring that will give some friction between the cams and will also hold them in place.

Each one of the cams will have one tooth per side; when the cams turn, the teeth will then engage.

What the cams do is control a latch that engages the hasp of the lock by one end. Along with a tooth on each side, the cams also have an indentation; when the indentations align, the latch can fit into the space that’s created and the hasp is released.

How it works

All of us who’ve used a combination lock know the routine: two full clockwise rotations of the dial to the first number in the combination, a counter-clockwise turn past the first number to get to the second number, then clockwise movement directly to the third number.

Turning two full clockwise rotations gets the three cams’ teeth aligned, and the second counter clockwise turn will only rotate the top cam. Once you turn past the original number, the tooth of the first cam will engage the second cam. The spring provides friction so that the third cam doesn’t move while the first two cams rotate. When you turn clockwise again, only the top cam will rotate. When the three indentations are aligned, the lock will release and open.

Hypothetically, a combination lock can contain as many cams as you like, depending on how secure you want the lock to be. However, for most people’s purposes, the three-cam lock has always been and will continue to be the market leader. To get the best quality combination lock, talk to a locksmith in Glendale if you live there or talk to an expert in your area. A locksmith in Glendale or experienced security professional will be able to recommend the best brand for your needs.

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