Almost all combination locks, including safe locks, operate on the same basic principle. The dial is turned to a preselected series of numbers that line up the unlocking mechanism and allow the lock to open. People always lose the combinations for these locks.
A common method of opening is to drill a small hole in the case to trip the locking mechanism, or read the combination. Some locks can be opened by rapping the case with a soft face hammer or wooden mallet. Others can be opened by codes, but only if you have a code book.
It is highly suggested buying a master padlock and peeling the back cover off of it to reveal the internal mechanisms. You should be able to identify: the shackle, locking pawl, locking dog, and three tumbler gates. Each manufacturer will have some variation of the actual construction, however, they all operate in almost the same manner.
There are four methods commonly used to open combination locks, 'Master Combination Locks' will briefly discuss all four methods.
Following matter is discussed in this paper:
- Drilling Method #2 (Master)