SCHLAGE HIGH SECURITY: Upgrading Primus to Primus XP

Feb. 1, 2008
The original Schlage Primus patent expired in 2007. New Primus XP patents extend through 2024. To gain additional patent protection, Schlage added a seventh depth finger pin and compatible side milling cut in the Primus key.

Schlage introduced the Primus™ high security lock cylinder during the fourth quarter of 1988. Schlage Primus was introduced with key-in-knob/lever, rim and mortise lock cylinders. Primus was Schlage Lock Company's entrance into the high security market place with patent protection.

The Primus cylinder incorporates two independent lock mechanisms having a total of 11 pin tumblers. These are the Schlage six-pin tumbler mechanism and a five finger pin mechanism that operates a sidebar. The pin tumblers and the sidebar create the two shear lines. The six spring-loaded pin tumblers provide security by extending across the shear line requiring the correct bitting configuration in order to align the pin tumblers. There are ten depths of cut (numbers 0-9) for the Schlage pin tumbler locks.

Five spring-loaded finger pins are contained in each Primus lock cylinder. The finger pins are controlled by the key's side millings and function like wafers in a wafer sidebar lock. Each finger pin has an extension that contacts the blade of the key. Each of the five finger pin locations are spaced between each six adjacent pin tumbler chambers.  

The original Primus patent incorporated six finger pins (numbers 1-6). Each finger pin has a depth of cut; either shallow or deep. In addition, each finger pin has an angle; either left, center or right. The number one finger pin is shallow and has a left angle of cut. The number two finger pin is deep and has a left angle of cut. The number three finger pin is shallow and has a center angle of cut. The number four finger pin is deep and has a center angle of cut. The number five finger pin is shallow and has a right angle of cut. The number six finger pin is deep and has a right angle of cut.

As the properly cut key is inserted into the keyway of the compatible lock cylinder, the pin tumblers raise and lower according to the bitting configuration. At the same time, the finger pin extensions contact the key blade, raising up and following the side milled cuts. In addition to raising the finger pins to the correct height, the root of each side cut swivels the finger pin extension to one of three positions: left, center or right. When this key is fully inserted, the finger pin gates align with the sidebar notches, creating a pocket for the sidebar to retract into the body of the plug as it rotates. The pin tumblers align at the shear line. The key can be turned, rotating the plug and operating the locking mechanism. The pin tumbler lock mechanism and finger pin lock mechanism are designed to only be operated by a properly cut, patent protected Schlage Primus key.

Patented Primus keys are designed to enter the keyway and operate both Primus and conventional lock cylinders having compatible keyways and bitting configuration for the pin tumblers and finger pins. This ability enables Primus locks and keys to be retrofit into existing Schlage key systems providing high security options as well as the capability to expand the system. To prevent unauthorized duplication of Primus keys, Schlage standard keys will not to enter Primus lock cylinder keyways.

NOTE: All Primus keys are pre-cut with the specific side milling.

The original Schlage Primus patent expired in 2007. New patents have been issued providing patent protection through 2024. This new patent protection has been incorporated into the name Primus XP. To gain the additional patent protection, Schlage Lock Company has made a number of additions, including a seventh depth finger pin and compatible side milling cut in the Primus key.

The 7-pin has a unique angle and milling location that provides an additional level of security. The 7-pin can be installed into existing Primus systems, converting them to XP. This brings the Classic Primus XP sidebar combinations to 7812. Converting an existing Primus system to a Primus XP system requires a new side bar milling having at least one 7-pin finger pin and a new Primus key with new side milling compatible with the change of finger pin(s).   


To convert a Primus lock cylinder to a Primus XP lock cylinder, the sidebar and one or more finger pins must be changed to match the new side milling of the replacement Primus XP keys.

Before recombinating the finger pins, we will discuss reading the finger pins by determining the depth and the angle. To determine the angle, the finger pin should be held using a pair of tweezers by the gate. The gate is the cut-out in the finger pin onto which slides the notch in the side bar. The position of the extension determines the angle. Hold the tweezers horizontal with the finger pin extension on the bottom. If the extension points towards the right of the tweezers, the finger pin is right. If the extension points away from the tweezers, the finger pin is center. If the extension is towards the left of the tweezers, the finger pin is left.

Once the angle has been determined, the next step is to determine the depth. There are actually three depths of cut. The deep cuts, left finger pin number 2 and right finger pin number 6, have the gate closest to the top of the pin. The center finger pin number 4 is the one-half increment lower, but is still a deep cut.

The center finger pin (number 3) has the gate closest to the bottom, making this finger a shallow depth. The three remaining finger pins are shallow cuts; left finger pin number 1 and right finger pin number 5 have their gates one half increment higher than the number three finger pin. The right finger pin number 7 has its gate one-half increment higher than the number 1 and number 5 finger pins. This additional height of the key milling requires a new key blank in order to create a side milling having a number 7 finger pin.


Keying a Primus lock cylinder for most standard applications does not require changes to the finger pins or sidebar. However, to simplify the keying procedure and eliminate problems that can occur with a sidebar, springs and finger pins mishap, I strongly recommend obtaining and using a Schlage 40-066 Plug Holder when rekeying Primus or Primus/Everest lock cylinders. This Plug Holder has grooves at 3 and 9 o'clock in order to accommodate operating the plug using a Primus key, loading finger pins or pin tumblers and generally keeping all of the components together.

When loading an empty Primus plug, begin by making sure the five finger pins agree with the five depths of cut in the side milling of the key. Once the five finger pins have been determined:

Step 1. With no key and no bottom pins in the plug, insert one spring into each end of the side bar slot in the plug.

Step 2. Place the sidebar against the two sidebar springs in the body of the plug and keep these pieces in place. The sidebar must press into the body of the plug in order to enter the Plug Holder.

Step 3. Beginning with the rear, slide the plug completely into the Plug Holder with the keyway upside down and the side bar sliding into the 9 o'clock groove.

Step 4. Insert one finger pin spring into each of the five finger pin chambers.

Step 5. Choose the five finger pins that will accommodate the milling positions in the side of the key.

Step 6. Beginning at the bow of the plug, insert the first finger pin into the into the pin chamber. Use your finger to keep the first finger pin within the plug.

Step 7. Insert the Primus set-up key into the plug just far enough for the side bitting to keep the first finger pin in place. The tip side milling does not have to be the same depth and angle of the finger pin.

Step 8. Insert the next finger pin into the plug and slide the set-up key in one cut further in order to keep the finger pin in place.

Step 9. Repeat this three more times until all five of the finger pins are installed and the set-up key is completely in the keyway.

Test the operation of the finger pins by rotating the set-up key counterclockwise a few degrees. If the side milling depths and angles are the same as the finger pins, the plug will rotate forcing the sidebar to retract within the plug. If they are not, the plug will not be able to rotate. If the set-up key rotates, continue with Step 10. If not remove the finger pins and start over.

Step 10. Carefully rotate the plug counterclockwise 180 degrees until the pin chambers are vertical.

Step 11. Load each pin chamber with the correct bottom pin and if master keyed, the correct master wafer.

Step 12. Once each chamber is loaded, test the operation of the change key and the top master key. With either key inserted into the plug, only master wafers can be above the outer diameter of the plug.

Step 13. Using the set-up key, load the plug into the housing. Test the operation of the change key and the top level master key being careful the plug does not slide out of the housing.

Step 14. Assemble the lock cylinder.

Note: When combinating a Primus lock cylinder, the pin tumbler springs are different from the finger pin springs, and are not interchangeable.

The Primus and Primus XP lock cylinders are available as controlled access and UL437. Primus cylinders are available as key-in-knob/lever, mortise, full size IC, rim, padlock and cabinet lock cylinders.

The patented Schlage Primus XP lock cylinder's availability is controlled. The base Primus XP lock cylinders availability starts with a shared sidebar milling and no sole source relationship with your distributor or customer. The next level is a semi-restricted sidebar milling and a sole source relationship with your distributor. The remaining levels above this point are set by the degree of exclusivity and the accompanying restrictions. For more information, contact your local locksmith distributor or the factory.

For more information, contact your local locksmith wholesaler or Schlage , 111 Congressional Blvd., Carmel , IN 46032 . Telephone: 800-8471864. Fax: 800-452-0663. Web Site: