Internet websites are filled with information about lock picking and key bumping. In the last few years the security of pin tumbler lock systems has been brought into question. The public has known for many years that pin tumbler locks could be picked open by experts, but internet key bumping videos show young children quickly bumping open certain pin tumbler locks after only a few minutes of training.
Success in bumping exists because as a key is inserted into a pin tumbler lock, there is a direct action between the key, the bottom pins and the driver pins. If a key is inserted quickly, as when the key is hit with a blunt instrument, the top and bottom tumblers may bounce apart enough to allow the plug to turn.
The Internet key bumping phenomenon was quickly noticed by lock manufacturers. Some manufacturers developed variations either in driver pin shapes or spring strengths as the answer. Another solution was to add a sidebar locking feature and to completely remove the top driver pin. Since the shearline between the top and bottom pins was eliminated, the action-reaction between top and bottom pins was also eliminated.
Successful key bumping requires a slight turning pressure on the key during the bumping process. When sidebar locking is used, any turning pressure during key bumping actually the sidebar against the tumblers and tends to restrict tumbler movement.
Lock picking also requires the use of a tension wrench. Turning action of the tension wrench holds a partial group of tumblers at the shearline while other tumblers are being manipulated. GM sidebar locks introduced seventy years ago had serrations on the mating surface of the lock tumbler. When a tension wrench was used, tumbler and sidebar serrations interlocked and prevented the tumblers from being easily moved to the real unlocked position. Sidebar construction deters both picking and bumping to a great extent.
Another angle to this story is being able to change combinations without disassembly. Locksmith Ledger has printed many rekeyable articles including locks such as U-Change and Mosler safe deposit locks.
Kwikset introduced the SmartKey rekeyable system in 2007. Basically the Kwikset system consists of three main parts, tumblers, racks and a sidebar. The tumbler contain a finger which connects into slots in the corresponding rack. Slots in the rack are .023 apart which is the depth increment for Kwikset. During rekeying the racks are held in the unlocked position and tumbler fingers are separated from the racks. When inserted, a new key will hold the tumblers in the new combination. As the new key is turned back to the locked position, the fingers again interlock with each rack and the new combination is set.
Schlage has recently introduced their SecureKey rekeyable system. Kwikset requires a probe tool to set the lock to the rekeying position while Schlage uses a special key to set the lock in the unlocked position. The special key must have the same cuts as the current operating key. Once the special key is turned and removed, the tumbler fingers are separated from the rack just as with the Kwikset system. Schlage racks uses slots which are .015 apart corresponding to normal Schlage increments.
Both Schlage and Kwikset offer keyable cylinders in popular deadbolt, lever and knob locks and at no extra charge. Weiser, a sister company to Kwikset, offers the same Kwikset rekeyable locks under the Weiser brand name but with the Kwikset keyway. Master Lock also offers a rekeyable deadbolt which uses the same depth, spaces and keyway as Kwikset.
The only drawback to rekeyables is that they cannot be masterkeyed, but for most residential situations, masterkeying is not a requirement.
Rekeyables mark a new era in locksmithing. The new features should make these products easy to sell, but your customer must be informed that a lost key situation may be more costly. Picking and bumping are not realistic alternatives in a lockout situation.
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