Anatomy of a Safe Lock: Three-Wheel Combination Locks Old and New

Tips for servicing three-wheel combination safe locks, old and new.


In order to do great work with safe locks, perhaps the most important thing to know is how the locks work.  Whether you’re diagnosing a malfunction, opening a safe with an unknown combination or performing maintenance or repairs, a thorough understanding of lock functionality is likely to...


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In order to do great work with safe locks, perhaps the most important thing to know is how the locks work.  Whether you’re diagnosing a malfunction, opening a safe with an unknown combination or performing maintenance or repairs, a thorough understanding of lock functionality is likely to take you much farther than any other information you could get your hands on.
So, in the interest of furthering education on that topic, this article will document the operational functionality of a few locks.  These are combination locks that I currently have in my possession:  a Kromer 8567, a Diebold 900, and an Ilco 6731.  They are similar in function, in that each is a three-wheel, direct-drive combination lock of fairly typical high-level design.  But even among these locks. there are significant differences that safe technicians should recognize.

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