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Posted by on February 15, 2008, 10:11 pm
wrote:
>Can one open a combination lock without knowing the combination?
>
>I'm helping to clear out a building which is about to be torn down,
>and in the office is a sheet metal cabinet, with a door on the left
>side and two shelves inside, and on the right side is a larger door
>with a safe-style lock on it, a single dial, a black plastic wheel
>with numbers on it.
>
>By no means is this worth the money that a professional would charge
>-- we never even locked it when we were using the building, or we
>would still remmeber the combination -- but it seems like a
>challenging project to me.
>
>It got locked somehow and no one remembers the combination. I've
>heard that it is still possible to open them. That the movies are not
>entirely wrong, with someone using a stethoscope to hear the
>"tumblers" "fall" into place.
>
>OTOH, I had a toy safe, when I was about 20 years old, twenty!, and it
>was clear plastic inside, and I could see the gears turn when I turned
>the dial on the front, and even in this toy, there were no tumblers to
>fall as one or more of the three wheels (the gears) each with a notch
>in one place, got their notches lined up. Only when all three notches
>were lined up, could one open the plastic safe.
>
>There was nothing to hear until the last second when it opened.
>Rotating the knob and the gears made no special noise at any point
>(except maybe a noise could be heard after one reversed direction of
>the knob and when a cog on a gear close to the front hit a stop on the
>next gear back and it started to turn. but what has the number that is
>at the top of the dial at that moment got to do with the combination
>number? Is that it? Can the latter be deduced from the former?) I
>don't see how it could be.
>
>From Wikipedia "Some rotary combination locks can be manipulated by
>feel or sound in order to determine the combination required to open
>the safe. More sophisticated locks use wheels made from lightweight
>and soft materials such as nylon, which reduces this vulnerability."
>This seems like nonsense. Why does it have to be "sophisticated" when
>my 4 dollar plastic toy safe couldn't be opened by feel or sound?
>
>One webpage says "Despite the tried-and-true design of the safe, it
>contains a fundamental weakness: Every safe must be accessible to a
>locksmith or other authority in the event of a malfunction or
>lock-out. This weakness forms the basis of safecracking." It says
>"every" but does that really apply to something that probably costs no
>more than one or two hundred dollars new now.
>
>BTW I don't think this is a fire safe or a real burglary safe. It
>bangs too much to have fire insulation in it (and I saw it when it was
>unlocked and open, come to think of it) and anyone could cut into it
>with a hack saw, or a boy scout can opener, or puncture a hole with a
>big screwdriver.
I doubt there are any "tumplers" in any safe that fall. I figured out
the combo for a fairly expensive (open) Mosler safe and it was a
pretty simple mechanism, similar to your toy safe or a Master combo
padlock. Disks with slots and a pawl that was pushed into all of them
at once when they were lined up and you turned the handle
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