Peter Martin wrote:I am puzzled why Corbin would go to a system with fewer bitting depth (six) instead of the Russwin 10-depths. It appears to make masterkeying a simpler process.
Pete:
Your puzzlement about Corbin-Russwin's development of System 70 just means that you are at the beginning of your journey learning about the art and science that is masterkeying. So let's discuss System 70 vs. Pre-System 70:
The key points to Pre-System 70 are: Odds/Evens and multiples of 4 and Bitting Parity
So imagine that Pre-System 70 Corbin-Russwin is like a Schlage master keying system. You have 10 depths but can only use half of them in any given pinning chamber of the lock: Odds and Evens, 1, 3, 5, 7, 9 or 2, 4, 6, 8, 0. Corbin's deepest depth was 0 (10) and in Russwin 0 was the shallowest depth.
Out of those five options in each bitting chamber one is reserved for your top master key of your system and thus leaves you with four bittings available to progress your change keys from.
Ex: 4 x 4 x 4 x 4 x 4 x 4 = 4,096 theoretical bittings possible in the system with six pin locks.
Next to consider is the bitting parity, this is the sequence of odds and evens in the key bittings in your system.
Examples:
OEOEOE
OOEEOO
EEOOEE
OOOEEE
EEEOOO
Bitting parity is particularly a concern when using a popular keyway in a large area. Locksmiths can prevent key interchange from occurring in the keying systems they produce by making sure not to repeat the same bitting parity in keying systems using the same commercial keyway. This is important because you do not want any random key off the street being capable of opening a lock in your building.
The key points of System 70 are: Doing more with less and multiples of 5
System 70 is like a Kwikset master keying system. You have 6 depths available in each chamber of the lock. You reserve on for your top master key and have five left to progress your change keys. 1, 2, 3, 4, 5, 6.
Ex: 5 x 5 x 5 x 5 x 5 x 5 = 15,625 theoretical bittings possible in the system with six pin locks.
Unfortunately you do not have bitting parity available to use as a tool to increase the security of your keying system.
With System 70 you want to make sure you are using a keyway that is as unique as it can possibly be as the likelihood that a random System 70 key that fits into your locks being able to operate one or more of them is about the same as the possibility that someone with a random Kwikset key can open your home's Kwikset lock installed on the door.
We have covered the differences in two bitting Systems developed by Corbin-Russwin. Let's go beyond the beyond here and mention the different bitting classes. X class, Z class, DH class are the three most common. X class and Z class are the old Corbin keyways with X class being the oldest and Z class beginning with the 59 series keyways in 1959. DH class are the old Russwin keyways still in common use, the D family and H family. There are others but they are much less common in modern systems (N class, A class, 981 class).
Now where Corbin-Russwin likes to get really complicated is that the locks over time have been made with different plug diameters for different types of locks in the different keyway bitting classes. This requires using pins of different sizes to key the locks correctly and having a very expensive OEM universal pinning kit to be able to do that properly.
~~ Evan
