At one time not too many decades ago there were dozens of individual lock companies in existence and each of them had their own keyway. It was a real challenge for locksmiths to memorize all those different keyways and to know exactly which blank to use for duplication. Combination changing was also a challenge as each lock company often used its own set of depth and spaces.
While the amount of domestic lock companies has decreased dramatically, overseas companies have more than made up for the drop in numbers. In almost every case, residential import locks are equipped with either SC1 or KW1 keyways. In addition, some remaining domestic companies offer residential locks with the same SC1 or KW1 as their standard keyways.
One definition for commodity is “a mass-produced unspecialized product.” With similarities in mechanical designs, mortise cutouts, knob or lever shapes plus copied keyways, most residential locksets have become commodities. Until you open the door and read a manufacturer’s name on the latch face, one lock brand looks like another from the outside of the door.
Locks are supposed to be made for their value as security items. According to my calculations, there are 6306 possible 5-pin KW1 key codes, assuming a 1-6 depth range, .088 cutter flats and a maximum adjacent cut of 4. 5-pin SC1 key codes produce 32,768 key codes assuming a maximum adjacent cut of 7 and eliminating 0 & 1 depths which have been seldom, if ever, used on residential locksets except for master key systems.
For every million KW1 locks sold, at least 158 will have the same combination. For every million SC1 locks sold, at least 30 will have the same combination. Just as a comparison, the Medeco code book contains over 7000 codes. Each code can use one of 729 different angle cuts. This produces approximately 4 million distinct key codes.
It would seem important for manufacturers of products which use SC1 or KW1 keyways to make their locks as secure as possible. This could be done either with new keyways, a change in depth increments or by making pin tumbler diameters smaller which would add more cuts per key. Every pin tumbler filing cabinet and mail box lock in existence uses smaller diameter .095 pins without a problem.
Possible key interchanges are either not a concern for manufacturers of locks using KW1 and SC1 keyways or perhaps the life cycle of pin tumblers locks is close enough to conclusion that increasing the security of pin tumbler locks may not be worth the investment.