In master

locksmithing Locksmithing is the science and art of making and defeating locks. Locksmithing is a traditional trade and in many countries requires completion of an apprenticeship. The level of formal education legally required varies from country to country ...

, 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. It can also refer to the measurable difference between a key and the size required to fit and operate the

keyway Keyway may refer to: *A part of a keyed joint used to connect a rotating machine element to a shaft; see key (engineering) *A keyhole, a hole or aperture (as in a door or lock) for receiving a key; see lock and key A lock is a mechanical or elec ...

of its paired

lock Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''Lock ...

. No two copies of keys are exactly the same, even if they were both made from

key blank Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (ma ...

s that are struck from the same mould or cut from the same duplicating/

milling machine Milling is the process of machining using rotary cutters to remove material by advancing a cutter into a workpiece. This may be done by varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of d ...

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 of an object, and its actual manufactured size. In locksmithing, the allowable tolerance 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 to (accuracy within 0.75% to 1.75%) in order to operate.

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 Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, ...

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

External links

History of locks

Technical requirements for DIN EN1303 and DIN 18252
{{Locksmithing Locksmithing Locks (security device) Engineering concepts Mechanical standards

Other applications

See also

References

External links