Key relevance

Key Relevance Diagram

In master locksmithing, key relevance is the measurable difference between an original key and a copy made of that key, either from a wax impression or directly from the original, and how similar the two keys are in size and shape.^[1] It can also refer to the measurable difference between a key and the size required to fit and operate the keyway of its paired lock.

No two copies of keys are exactly the same, even if they were both made from key blanks that are struck from the same mould or cut from the same duplicating/milling machine with no changes to the bitting settings in between. Even under these favorable circumstances, there will be minute differences between the two key shapes, though their key relevance is extremely high.

In all machining work, there are measurable amounts of difference between the design specification^[2] of an object, and its actual manufactured size. In locksmithing, the allowable tolerance^[3] is decided by the range of minute differences between a key's size and shape in comparison to the size and shape required to turn the tumblers within the lock. Key relevance is the measure of similarity between the key and the optimal size needed to fit the lock, or it is the similarity between a duplicate key and the original it is seeking to replicate.

Key relevance cannot be deduced from a key code, since the key code merely refers to a central authoritative source for designed shapes and sizes of keys.

Typical modern keys require a key relevance of approximately 0.03 millimetres (0.0012 in) to 0.07 millimetres (0.0028 in) (accuracy within 0.75% to 1.75%) in order to operate.^[4]

Other applications

"Key relevance" may also be applied to types of electronic locks when used to refer to similarities in magnetic signatures or radio codes, though truly digital-coded radio signals do not have key relevance ratings because they must have precise unlocking codes, with no degree of difference whatsoever in order to operate.

The term has also occasionally been co-opted by broader mechanical engineering to refer to the similarity of fit between two interlocking machined parts, although "tolerance" or "backlash" has gained far wider adoption and acceptance in usage.

References

↑ Mick, Friend (2004). "The Encyclopaedia for Locksmiths". The Encyclopaedia for Locksmiths. New York: Authors On Line, Limited. ISBN 0-7552-0117-5.
↑ ASTM engineering specification standards
↑ Conway, Hugh Graham (1966). Engineering Tolerances: A Study of Tolerances, Limits and Fits for Engineering Purposes, with Full Tables of All Recognized and Published Tolerance Systems (Third ed.). London: Sir Isaac Pitman & Sons Ltd.
↑ Rudman, Jack (1985). This is Your Locksmith Passbook. National Learning Corp. ISBN 0-8373-1348-1.

Locksmithing & Lock picking

Topics	Electric strike Key control Key relevance Lock bumping Lock picking Lockout-tagout Maison key system Rekeying Single-point locking Three-point locking

Components	Bitting Bolt stump Break Interchangeable core Key blank Key code Keyhole Lockset Shear line Split pin

Key types	Berlin key Bump key Change key Master key Skeleton key Smart key Tubular key Transponder key

Mechanical Locks	Bored cylindrical lock Bramah lock Cylinder lock Disc tumbler lock Key retainer Lever tumbler lock (Chubb detector lock) Magnetic-coded lock Magnetic keyed lock Mortise lock Padlock Combination lock Rotary combination lock Time-delay combination locks Pin tumbler lock (snib) Protector lock Relocking device Time lock Tubular pin tumbler lock Warded lock Wafer tumbler lock

Electronic Locks	Electromagnetic lock Electronic lock Electric strike Magnetic-coded lock Keycard lock Electronic/digital-cylinder pin tumbler lock

Specific lock types	Bicycle lock Chamber lock Child safety lock Dead bolt Keycard lock Kensington Security Slot Luggage lock Power door locks The Club TSA lock

Tools	Lockpick Slim Jim Snap gun Tubular lock pick

Related	Bolt cutter Door chain Exit control lock Famous locksmiths Interlock (engineering) Keychain Key (engineering) Lock manufacturers Lock puzzle Lock snapping Locksport Two-man rule

Category:Locksmithing Keys Locks Book

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Key relevance

Other applications

See also

References