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On the Construction of Locks and Keys by John Chubb
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28 CONSTRUCTION OF LOCKS AND KEYS.
the tumblers was lifted too high, it overset the detector detent, which by a spring action fastened the bolt, so as to secure it from being afterwards withdrawn; and although the bolt should be released from all obstruction by the other tumblers, the fastened tumbler would of itself continue to hold the bolt, as an additional detention, not capable of being removed, even by an ordinary application of the true key, which would not go round in the lock, after the detector was brought into action; and thus notice was given, that a fraudulent attempt had been made to violate the lock. To set the detector free, the true key required to be first turned partially round, in a reverse direction, whereby the detector was restored to its quiescent position, and then the true key would operate in the usual manner. It was only by overlifting any one, or more of the tumblers, that the detector could be brought into action, and the use of the true key could never overlift any tumbler, or disturb the detector.
In making a false key, the bit was usually left rather too long, being gradually reduced by trial until the proper length was attained. Though this process might succeed with a common lock, it had no chance with Chubb's lock, which would become detected by one trial with a false key, having even but one step too long, and if a step was too short at first, it was not easy to lengthen it. Hence the maker of a false key was beset with difficulty at every stage of his operations; and without tolerably accurate information respecting the true key, it was scarcely possible to find out the combination of the six tumblers, or to avoid bringing the ' detector' into action anvilfire.
Mr. CHUBB said, in reply to Captain Moorsom, that if a lock had only one key, and it should happen to be lost, when the lock was fastened, the door would require to be forced open, but good locks generally had two keys, one of which was deposited in a place of safety. Two hundred and twenty locks might be made with one keyhole, and a separate key to each, yet having one master key for the whole ; but if a greater number was required, it. would be necessary to have two keyholes. In the event of the master-key being stolen, he knew of no remedy, but replacing the locks, or altering their combinations.
It was impossible to take a sufficiently correct impression, in wax, for the purpose of making a false key, as the locks were manufactured with such delicacy and nicety, that the slightest alteration, or difference in the key, would prevent the lock being opened by it.
Mr. VABLEY thought, that Somerford's lock was equal to Mr. Chubb's, and had double the power, as a key was weakened by the
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On the Construction of Locks and Keys by John Chubb