The dial turns, the numbers are right, nothing happens
Mechanical safe locks fail far less often than people think. What fails is the dialling: the sequence has a specific number of passes for each digit, and one miscount produces exactly the symptom you are looking at.
The sequence, on a standard three-wheel lock
Written for the common right-hand dial with numbers 0–99, such as the Sargent & Greenleaf 6730 family. Your lock may differ — check the maker's sheet on the lock library page.
- Clear the lock Turn the dial left (counter-clockwise) at least four full turns. This picks up all the wheels and cancels whatever position they were in.
- First number — the fourth time you reach it Keep turning left, counting each time the first number of the combination passes the index mark. Stop on it the fourth time.
- Second number — the third time Now turn right (clockwise). Pass the second number twice and stop on it the third time.
- Third number — the second time Turn left again and stop on the third number the second time it reaches the index.
- Retract the bolt Turn the dial right slowly until it stops. Then turn the handle. If the dial stops short and refuses to go further, the wheels are not aligned — start again from step one.
Overshooting a number by even one graduation and then backing up. A mechanical lock does not accept correction: turning back leaves the wheel in the wrong place. If you pass the number, you have to start from step one. Not from the previous digit — from the beginning.
If a correct sequence still fails
Try the numbers one graduation either side
Dials drift with age and wear. Many locks that “stopped working” open on ±1 from each written number. Work through the combinations methodically: first number −1, then +1, then the same for the second, then the third. Slowly — a rushed dial is a wrong dial.
Check whether the dial itself is loose or slipping
Hold the dial ring and turn the dial. Any play between dial and spindle means the numbers you see no longer correspond to the wheels inside. That is a mechanical repair, not a dialling problem.
Listen for the dial going dead in one direction
A dial that spins freely without the faint resistance of the wheel pack — or that turns endlessly past its normal stop — usually means a broken spindle or a detached drive cam. Technician.
Combination written by a previous owner
Inherited numbers are often recorded in the wrong order or from a different safe. If three attempts fail with an inherited combination, treat it as an unknown combination rather than a fault.
A number between 5 and 11 on the third position
Some locks are not permitted to have the third number in the forbidden zone around the dial's spline — on S&G locks splined at 50, the third number must not sit between 5 and 11. A combination set there works unreliably, and a lock set that way by a previous owner will one day not open at all. Worth having changed even after it opens.