Key for rotary plug and cylinder lock, and method of forming the key

Abstract

A difficult-to-duplicate key for operating a rotatable plug and cylinder lock has an imaginary center axis that extends along the length of the key at a location situated between opposed, relatively narrow edge surfaces, and centered between opposed, relatively wide side surfaces. The edge and side surfaces cooperate to define a key of generally rectangular cross section. First, second and third rows of concave recesses are formed in and extend lengthwise along the side and edge surfaces of the key for receiving rounded inner end regions of pin tumblers of the plug and cylinder lock when the key is inserted to an operating position in a keyway of the lock for positioning the tumblers to permit the plug to be rotated relative to the cylinder. The recesses of the first, second and third rows extend along first, second and third sets of recess axes that extend in first, second and third planes, respectively, that radiate from the imaginary center axis. Non-standard angular relationships of the first, second and third planes are utilized to orient the first, second and third sets of axes in a non-standard, non-symmetrical and non-aligned manner that causes the recesses of at least one (preferably two) of the first, second and third rows to be of a non-circular shape that is difficult to 'read' to determine the key's recess axis orientation. The use of difficult to 'read' recess shapes together with the use of non-standard recess axis orientations renders key duplication difficult.