sakana-lures said:
The tool you describe is called a change key and is available for most quality safe combination locks. If and when you change your combination, make sure you test it with the door open.
Locksmiths love charging clients who lock the safe door, then check the new combination to see if it works!
90% of locksmithing work is fixing other people's dumb mistakes.
"I locked my keys in my car"
"I went out to get the paper and accidentally locked the door on my way out"
<hands you a pile of parts> "I wanted to see how it worked"
<walk up to a lock with a piece of paperclip jammed inside> "so who's the macgyver wannabe?"
"the key wouldn't turn so I went and got the pliers..."
"the inside knob wouldn't come off so I tried to use a knitting needle"
"I made a bet with a friend...."
"I'm a retired locksmith ya know.... BUT..." (thats my favorite)
and the list goes on and on and on
every safe with a mechanical combination lock comes with a change key. unless you buy it at costco...

most people don't know what it is, and quickly throw it out. on the other hand, most people can't be bothered to learn how to change their combination. i get 5-6 calls a day of "i need my combination changed".... businesses and residential....
since you've brought this up, for anyone else who is just learning how to use their change key:
-input current combination and open safe door. without closing the door, turn the dial to lock it back up.
-if you look to the left of the index mark on the dial, you will see a smaller mark. this is the "change index". input your old combination AT THIS MARK. so instead of dialing the numbers to the mark that is straight upward, dial it to the mark that is to the left and 45 degrees away from where you normally input it. DO NOT MOVE THE DIAL AFTER HITTING THE THIRD NUMBER like you normally would.
-insert your change key into the small hole in the lock casing. turn the key 90 degrees. it will be a different way depending on how the lock is mounted. make sure the key is in there all the way. sometimes if the dial is old and has shifted or you went past a number by a tiny margin, you won't be able to put it in all the way. if so, start over.
- dial your NEW combination AT THE CHANGE INDEX. STOP ON THE FINAL NUMBER. move the dial 10 numbers TO THE RIGHT. STOP.
- turn your change key back 90 degrees. take it out.
- WITHOUT CLOSING THE DOOR, try your new combination at the OPENING INDEX (where you normally put in your combination). TRY IT AT LEAST 3 TIMES BEFORE CLOSING THE DOOR.
NEVER, UNDER ANY CIRCUMSTANCES, REMOVE THE BACK COVER OF A SAFE LOCK. If you just want to "see how it works" order what we call a "cutaway" off ebay. You can learn from one of those. Don't mess with a lock that you depend on. What will happen is you won't know how to put it back together, you'll leave to grab another beer to help clear your mind, the wife will come along and close the safe and the relocker will not allow you to get it back open. Then you will be on the phone with me, crying because I have to charge you 300$ + 45$ /hr to drill into your brand new 6,000$ Fort Knox gun safe.
Also, there is a range of numbers that should not be used as the last digit of your combination. This is due to mechanical reasons that you would understand if you saw how the lock worked. This varies from lock to lock. Find the manual for your specific lock and look for "the forbidden zone".
If anyone needs any help, feel free to shoot me a PM. I might be young, but I have a lot of experience with older safes as well, I've been working with safes since I was 13. A good 11 years now. Hand change models and the like, its all no problem. I can also get change keys for almost any safe, rare or the standard S&G group II 3wheel. Whatever you need.