Why We Don't Have To Spin the Dial on a Master Combination Padlock After Relocking It

On some combination locks, the user must spin the dial after the relocking. If the user fails to do so, the lock can be reopened without redialing the full combination, because the notches one one or more of the cams remain lined up under the pawl. As mentioned previously, the peg on the rear of the back cam has a function. When the shackle is pulled out of the lock, a bar attached to it, visible in the picture on the previous page, pushes this peg to move the back cam.This movement ensures that the cam's notch is no longer aligned under the pawl. This feature of the Master Lock eliminates the need to spin the dial.

You can observe the peg pushing the shackle, as follows, on some, but not all, Master locks: With the padlock unlocked, hold it vertically and gently drop the shackle into the lock, so it rests inside the lock, but the lock is not locked. Turn the dial left at least 2 turns and then turn the dial slowly. About 10 marks before the first number, the peg will engage and turning the dial will start pushing the shackle up. About 4 to 5 marks before the first number, the peg will move out of the way and the shackle will drop down.

It is still a good idea to spin the dial at least twice. If the dial is not spun, it remains at or very close to the last number in the combination. The middle cam remains in place, with its notch aligned under the pawl. If the dial is turned left, when the second number is reached, there is a slight increase in force needed to turn the dial because the peg on the front cam has met the peg on the middle cam, and we are now turning two cams instead of one. Furthermore, there is a click when the pegs meet, so, someone trying to work out your combination can listen for the click. The dial should be at the second number number when the click is heard. This method was enhanced. If the dial is held loosely and spun rapidly, there will be a louder click and the dial will slip in the fingers at the last number. The dial slips because the middle cam is not turning when the peg on the front cam strikes the middle cam's peg. The effect is similar to a cue ball hitting another ball dead-on in the game of pool. So, someone who wants to works out the combination will easily get the last two numbers. On the "old" locks that don't have 7 digit serial numbers beginning with 800, the combination is narrowed down to 8 possibilities (8 possible first numbers using the rules on the other pages.) On the newer locks, there are no more than 33 combinations to try.

For higher security applications of combination locks, such as safes, the manufacturers may have deliberately left out this feature, requiring the user to manually spin the dial for greater security.

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