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The Kid Should See This

How are combination locks made?

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How did Wild West safe crackers break into the bank safe mechanical combination locks? And what goes into the engineering inside the everyday combination locks like the ones we use on lockers?

In Nicholasville, Kentucky, one of America’s oldest lock manufacturers has been making locks, safes, and vaults since 1847. This Discovery UK introduces Sargent and Greenleaf co-founder James Sargent who “invented devices that defeated legendary Wild West bank robbers Frank and Jesse James.”

“So what’s going on behind this deceptively simple combination dial, numbered 0 to 99?”

hand assembly
American history + factories + engineering come together to share how things are made in this clip from How Do They Do It? It includes a behind-the-scenes tour that mixes heavy duty machines with hand-assembled components. A quick explanation from the video:

“The dial turns three wheels. These wheels all have an opening called a wheel gate. They’re attached to a brass ring called a drive cam with an indentation known as the drive cam gate. The lock bolt is connected to a lever with a bar, confusingly called a fence, attached at a right angle.”

how locks work

“Turning the dial first left, then right, then left again, according to the combination, lines up the wheel gates. When the correct numbers have been dialed in the correct order, the fence falls into place. The lever engages with the drive cam, and hey presto! The lock can now be opened.”

Bonus peeks at a few old combination locks, and a molten zinc alloyβ€”aluminum, magnesium, copper, and zincβ€”that’s used for the lock’s injection molded case.

molten metal alloy
Watch these handpicked videos next:
β€’Β How do locks work?
β€’Β Making a combination lock from a steel bolt
β€’ The mighty mathematics of the lever
β€’Β Why do tumbleweeds tumble?

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