Schlage Primus

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Schlage Primus

Schlage Primus
Schlage Primus cylinder.jpg
Name Schlage Primus
Manufacturer Schlage
Lock Type Cylinder
Lock Design Pin-tumbler, Sidebar
Security Rating(s) UL 437
Patent US 4,756,177
US 4,815,307

Expired 2007.

# of Components 6
Component Type Pin-tumbler
Related Locks
Schlage Everest
Schlage Everest 29 SL Primus XP

The Primus (or Classic Primus, Primus XP) is a UL 437-rated pin-tumbler lock made by Schlage. It uses six pin-tumblers and a sidebar that requires finger pins to be raised and rotated properly. The Primus is functionally identical to the ASSA Twin Combi lock, but it does not include as many anti-lockpicking and key control mechanisms. The patent protection on Primus keys ended in 2007. Primus XP was released on 11/08/2007 and is patented until 2024.

The Primus is an updated version of the Schlage Everest. The Schlage Everest 29 SL Primus XP is an alternate version of the Primus that enhances key control capabilities.

Principles of operation

See also ASSA Twin Combi

The Primus uses six pin-tumblers and five sidebar finger pins. Unlike its ASSA counterpart, the Primus does not provide any security pins by default. There are 10 depths available for bottom (key) pins. Key pins are numbered 0-9 sized .165" to .300 with a step of .015". There are eight master pins numbered 2-8 sized 0.030" to 0.135" with a step of .015". Driver pins come in three sizes (1-3) from .235" to .165" with a step of .035". These drivers provide pseudo-balanced pin stacks; a 1 driver is used if the size of the key and master pin stack is 0-3, 2 if 4-6, and 3 if 7-9. Any key/master pin stack larger than 9 is invalid (the master pin would not drop down far enough to align at the shear line. In total, there are 1,000,000 (106) theoretical key differs for the pin-tumbler portion of the lock.

The sidebar, located in the 8 o'clock position, is pushed out by two springs. The sidebar bitting on the key raises finger pins which interface with the sidebar. Sidebar finger pins must be raised and rotated properly for the sidebar to retract. When both the sidebar pins and the pin-tumblers are aligned the plug can rotate.


  • The Primus is available in rated and non-rated cylinders. Non-rated cylinders do not include hardened anti-drill protections.[1]

Key security levels

The Primus offers a variety of key security levels:

Level 1 - Commercially Exclusive
Distributors sell to end users via commercial locksmiths. All Level 1 keys have the same sidebar bitting code.[2]
Level 1+ - Wholesaler/Locksmith Exclusive
Locksmiths resell exclusive wholesaler sidebar bittings. Keys are stamped with unique locksmith ID numbers.
Level 2 - Contract Hardware Dealer Exclusive
Exclusivity limited to contract hardware dealers who sell directly to end users.
Level 3 - End User Exclusive
Exclusivity based on random assignment or the first 2 digits of a zip code.
Level 4 - End User Exclusive
Exclusivity based on time zone or nation.

Disassembly instructions

The Schlage Primus is disassembled in the same way as a traditional pin-tumbler cylinder. Care is taken to account for the sidebar and finger pins. Finger pins are spring biased outwards when the plug is exposed without a key inserted.

  1. Remove the cam or C-clip.
  2. Insert the key and turn the plug 45-90 degrees.
  3. Withdraw the plug from the cylinder. (A plug follower is recommended)


  1. Remove the chamber casings and take out each pin-stack individually
  2. Remove the cam or C-clip.
  3. Withdraw the plug from the cylinder.



  • Key bumping is possible only with a bump key that has the correct sidebar code.


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See also