Mastering IC Pin Stack Mathematics

Each IC lock manufacturer has its own pinning system. For locksmiths who service many different types of IC systems, it can be difficult to remember which pinning system to use.


Interchangeable core (IC) lock systems have been steadily gaining in popularity. IC locks were first brought to public attention by the Best Lock Company more than 70 years ago. Because IC cylinders can be immediately changed without major components being removed from the door, government...


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Interchangeable core (IC) lock systems have been steadily gaining in popularity. IC locks were first brought to public attention by the Best Lock Company more than 70 years ago. Because IC cylinders can be immediately changed without major components being removed from the door, government installations were often equipped with Best IC cylinders during World War II. After the war many peace-time applications were found and Best Lock developed sales for IC cylinder in commercial applications. The small format interchangeable core (SFIC) revolution was underway.

Other companies did try to follow the lead of Best Lock with removable core locks systems of their own. As example, Corbin had a system which used a round, removable cylinder which fit into a thin outer shell. This was usable for a mortise cylinder configuration but not easily adaptable to cylindrical door locks or cabinet hardware.

In order to make the SFIC cylinder compact enough to fit a variety of applications, the lock plug was made smaller than normal cylinders. The average plug diameter of most standard lock cylinders is approximately .500” while the Best Lock plug was .432”. Best Lock key blank dimensions were made small enough to fit into the smaller diameter plug.

Key blank sizes used by most other lock manufacturers were too large to fit into the smaller .432” diameter plug size without seriously weakening the cylinder plug. The solution was to make a Large Format Interchangeable Core (LFIC) cylinder to maintain lock dependability while allowing existing large key blanks to enter. While LFIC cylinders will not fit into SFIC housings, at least these lock companies can offer a comparable removable core system to their customers.

Each IC lock manufacturer has its own system of pinning. If you are an institutional locksmith and only work on one brand of locks, you can quickly learn how to pin that system. But when you are asked to work on many different types of IC systems, it is sometimes difficult to remember which pinning system to use.

Most IC cylinders consist of three main parts: lock plug, lock sleeve and lock body. The lock sleeve contains a lug which projects out of the lock housing and retains the IC core cylinder within the main lock cylinder housing. Basically the lock plug fits into the lock sleeve and both parts then fit into the lock body. When an operating key aligns pins at the lock plug shearline, the plug can turn. When a control key aligns pins at the lock sleeve shearline, the sleeve can turn. The sleeve is designed to rotate just far enough to move the locking lug within the lock body so the IC cylinder unit can be removed. Some manufacturers such as Yale and Schlage use variations of the locking sleeve design, but produce to same result of simple removal and insertion of the IC cylinder.

Following are the equations for pinning many common cylinders.

BEST A2

1) (A)= total of bottom pin and master pin numbers

2) (B)= “10” plus control key cut

3) (C)= (B) minus (A) [C= control pin number]

4) (D)= 23 minus (C+A) [D= top pin number]

Pinning: A+C+D

Note: Several companies such as Kaba Peaks, Keymark products and CX-5 have special keyways, but use the same spacing, depth and pinning numbers as shown for the A2 system. Other companies such as Arrow, Falcon and KSP offer the A2 system with industry standard keyways.

BEST A3

1) (A)= total of bottom pin and master pin numbers

2) (B)= “7” plus control key cut

3) (C)= (B) minus (A) [C= control pin number]

4) (D)= 16 minus (C+A) [D= top pin number]

Pinning: A+C+D

BEST A4

1) (A)= total of bottom pin and master pin numbers

2) (B)= “6” plus control key cut

3) (C)= (B) minus (A) [C= control pin number

4) (D)= 14 minus (C+A) [D= top pin number]

Pinning: A+C+D

CORBIN/RUSSWIN (spaces 1,6 [& 7 if used])

1) (A)= total of bottom and master pin numbers

2) no control pins are used

3) (B) .247 top pin (in all cases)

Pinning: A+B

CORBIN/RUSSWIN (control lug spaces 2,3,4,5)

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