Keying the Corbin Figure 8 Style Removable Core

Corbin first introduced their version of the removable core lock mechanism during the early 1960s with what is known as the “Old Round Core.”  This five- or six-pin tumbler removable core system was similar to several lock manufacturers’ products at the time. Unlike removable and...



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Corbin first introduced their version of the removable core lock mechanism during the early 1960s with what is known as the “Old Round Core.”  This five- or six-pin tumbler removable core system was similar to several lock manufacturers’ products at the time. Unlike removable and interchangeable core lock mechanisms in use today, the “Old Round Core” was almost the size of a mortise cylinder. In fact the face of the core (known as a shell) was the same diameter. The housing was the size of a mortise cylinder with just a thin wall that the core slid into. To remove the core, only the last pin chamber was operated by the control key.

Editor’s Note: For the purpose of this article, we will be discussing the factory approved method of keying the Corbin Figure 8 Removable Core lock mechanism.

The “Old Round Core” was phased out with the introduction of the Corbin Figure 8 Style Removable Core Lock Mechanism during the early 1970s. The Corbin Figure 8 style removable core is similar in shape to the Best/Falcon interchangeable core; however it has a larger diameter body will not fit into the Best/Falcon housings. Unlike the Best/Falcon core, the Corbin Figure 8 style contains both one and two shear line pin chambers. The operating shear line is the plug shear line. The control shear line, located above the plug shear line, controls removal and insertion of the core into the housing by rotating approximately 15 degrees clockwise.

Four control chambers in spaces 2-3-4-5 have two shear lines. The remaining chambers have only one shear line. They are in positions 1 and 6 for a six-pin core and 1, 6 and 7 for a seven-pin core. These pin chambers are combinated like a conventional pin tumbler lock using only top, master (if master keyed) and bottom pins.
A unique feature of this core mechanism is the tabs that extend from the top of the control sleeve and align with each of the four pin chambers. These tabs control the rotation of the control sleeve by using the top pins to obstruct further movement.

An early version of the Corbin Figure 8 style removable core was produced until the mid-1980s. This version made use of a saddle style control, not a complete sleeve. The saddle style control depends upon the pin tumblers to keep it in place.

The control sleeve version was introduced in the mid-1980’s and replaced the saddle sleeve. Both of these versions have four control chambers in spaces 2-3-4-5. Pin lengths and pinning rules are identical for both systems.
Note: The keyways used for the Corbin Figure 8 style removable cores are mainly the same as those used by Corbin conventional and Master Ring cylinders.

In 1993, Corbin and Russwin were consolidated into one company. Since the companies were at one time separate, they each have separate histories and many different pin lengths and pin length modifications were introduced over the decades. This can result in difficulty when combinating a Corbin, Russwin or Corbin Russwin lock cylinder using an existing bitting configuration.

For this reason, Corbin Russwin recommends using factory length pinning kits. The .003” and .005” generic pin kits may not always provide the same results as a factory length pin kit. Also, originated or duplicated keys must be cut as accurately as possible. Keys with wear should not be duplicated. Replacement keys should be originated to ensure proper operation.

For the purpose of this article, we will be discussing the Corbin Z (Russwin DH) Class- System 70. This one step master key system incorporates six depth increments 1-6, having a drop of approximately .028”.
The bottom pin lengths using the .509” diameter plug are:

1- .160”           2- .189”           3- .217”
4- .245”           5- .273”           6- .301”
Note: The drop is not always .028” between adjacent pin lengths.
The six top pin lengths for the pin chambers 2-3-4-5 in the Figure 8 Removable Core are:
1- .192”           2- .163”           3- .135”
4- .107”           5- .080”           6- .080”

For the non-control pin chambers (1 & 6 or 1, 6 & 7), the top pin length is always .247”.

Ten Build-up Pin lengths can be used in pin chambers 2-3-4-5. These control pin dimensions do not follow any incremental order. To combinate a Corbin Figure 8 Style Core, Corbin set the start dimension to zero. Then all of the Build-up Pins were either a positive number or a negative number.

-4 .051”           -3 .080”           -2 .107”          
-1 .135”           0 .163”
+1 .192”          +2 .218”          +3 .247”         
+4 .275”          +5 .303”

IMPORTANT: The non-control pin chambers (1 & 6 or 1, 6 & 7); do not have Build-up Pins as there is only one shear line.

When rekeying IC cores, a good way to be sure a master key, control and change key will operate is to pin one chamber at a time. This way, if there is a problem, it is not necessary to empty all of the pinned chambers. Only the last chamber pinned will have to be emptied.

When testing the chambers, hold the springs in position with your thumb or finger. Test each pinned chamber with a master key, preferably the AMK (Absolute Master Key), the control key and a change key. If the three keys operate the core, combinate the next chamber. 
IMPORTANT: Early Corbin key codes usually stamped into the bow of the key are written from tip to bow. Later key codes are from bow to tip.

Combinating the Corbin Figure 8 style removable core requires two pinning methods - combinating the non-control pin chambers and the control pin chambers. Combinating the non-control pin chambers (1, 6 & 7) is identical to combinating a conventional lock cylinder.

The bottom pin is the shallowest depth of cut between the AMK and the change key. The AMK and the control key will normally have identical depths of cut in spaces 1 & 6 or 1, 6 & 7. The master pin, if required, is the difference between the deep cut and the shallow cut. The top pin for these pin chambers is .247”.

Combinating the control pin chambers (2-3-4-5) uses the same steps for choosing the bottom pin and master pin (if required) as the non-control pin chambers. The top pin length number is the same as the control bittings. The Build-up Pin equals the control cut number minus the plug total. The plug total is the master pin number plus the bottom pin number. The plug total is then subtracted from the control cut number, permitting the Build-up Pin to be either a positive or negative number.

For an example, we will use the following:

Control Key                563421
Top Master Key                      525341
Change Key                541563

Pinning the number one chamber, the bottom pin is a 5. There is no master pin and the top pin is a .247”. This is because the number one pin chamber is non-control.

Pinning the number two chamber, the bottom pin is 2. The master pin is 2. The plug total is 4. The control cut (6) minus the plug total (4) is +2. The Build-up Pin is +2.

Pinning the number three chamber, the bottom pin is 1. The master pin is 4. The plug total is 5. The control cut (3) minus the plug total (5) is -2. The Build-up Pin is -2.

Pinning the number four chamber, the bottom pin is 3. The master pin is 2. The plug total is 5. The control cut (4) minus the plug total (5) is -1. The Build-up Pin is -1.

Pinning the number five chamber, the bottom pin is 4. The master pin is 2. The plug total is 6. The control cut (2) minus the plug total (6) is -4. The Build-up Pin is -4.

Pinning the number six chamber, the bottom pin is 1. The master pin is 2. The top pin is a .247”. This is because the number six pin chamber is non-control.

The core will be combinated using the following length pins:
Top Pins          Std*      6        3         4         2         Std*
Build-up Pins  ---        +2       -2         -1         -4         ---
Master Pins     ---          2        4         3         2         2        
Bottom Pins    5           2        1         5         4         1
Std* indicates the .247” top pin.

The Corbin Z (Russwin DH) Class- System 70 incorporates the following listed keyways and certain restricted keyways.
60        59A1   59B1               59C1               59D1
70        59A2   59B2               59C2               59D2
D1 thru D4      H1 thru H8      L1 thru L4

For specific dimensions, keyway and key blank information, we have used the Corbin Russwin Cylinder Manual, sixth edition as a reference.

For more information, contact your local locksmith distributor or Corbin Russwin Architectural Hardware, 225 Episcopal Road, Berlin, CT 06037-4004. Telephone: 800-543-3658. Fax: 800-447-6714. Web Site: www.corbinrusswin.com.      

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