Servicing Schlage Primus / Primus XP Lock Cylinders

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. The Primus cylinder is a modified six-pin tumbler conventional Schlage lock cylinder. A sidebar operated by five finger pins provides the additional level of security. To accommodate the five finger pins, a Primus key has a secondary bitting on the side of the blade.

Each Schlage Primus key has the word “Primus” stamped into the back of the pyramid-shaped key bow and lock cylinders have “Primus” stamped into the face of the plug. When a properly cut Primus key is inserted into a properly combinated Primus lock cylinder, each of the side bitting under cuts lift and rotate the finger pins until their notches (in the back of the finger pins) align with the notches in the side bar. When all of the notches align, the side bar retracts into the body of the plug. With the regular pins aligning at their shear line, the plug is free to rotate and operate the locking mechanism.

Primus was Schlage’s entrance into the high security market place with patent protection. The Primus line has expanded to include conventional (key-in-lever and knob) cylinders, mortise cylinders, rim cylinders and large format interchangeable core. The original Primus patent, U.S. 5,715,717 has expired. In 2007, Schlage patented the Primus XP high security lock cylinder. As part of the new patent, a seventh finger pin was added, providing additional security.

Schlage Primus and Primus XP lock cylinders ‘six -pin tumbler specifications are identical to the Schlage Classic, from bottom, top and master pins to springs and key cutting. Schlage Primus and Classic six-pin tumbler bitting instructions include using the three lengths of top pins.

The original Primus patent has six finger pins, differentiated by depth and angle. They are:

• Finger Pin 1: Angle Left, Depth Shallow
• Finger Pin 2: Angle Left, Depth Deep
• Finger Pin 3: Angle Center, Depth Shallow
• Finger Pin 4: Angle Center, Depth Deep
• Finger Pin 5: Angle Right, Depth Shallow
• Finger Pin 6: Angle Right, Depth Deep

With Schlage patent number 7,159,424, Primus XP has incorporated a #7 finger pin that provides additional security. Patent protection is into 2024. Finger Pin 7’s Angle is Right and Depth is Extra Shallow.

To read the finger pins, hold a finger pin with a pair of tweezers using the two side bar cutouts. Hold the finger pins vertical with the pointed tip down. If the pointed tip is slight turned to the left, it is a left angle finger pin. If the pointed tip is slight turned to the right, it is a right angle finger pin. If the pointed tip is straight away, it is a center finger pin.

Finger pin depth is determined by the proximity of the cutouts to the pointed tip. If cutouts are closer to the tip, the finger pin is shallow (or extra shallow XP). If notches are farther away from the pointed tip, the finger pin is deep.

All Schlage Primus and Primus XP keys have six pin tumbler cuts and five Side Bit cuts that are read from bow to tip. When a Primus key is inserted into a lock cylinder, each side pin cut in the key raises and swivels the finger pin in order to align the notches in the pin with the notches in the side bar. This means that each side bit cut is read from the lowest point to adjacent high point.

There are three high point heights. A number two, four or six finger pin has a deep cut just above the base of the blade (lowest). A number one, three or five cut is shallow, having the side bit cut not as deep (middle). A number seven finger pin has the side bit cut with the shallowest bitting (highest).

An improper finger pin will not be at either the correct height or angle for the side bar. If the two notches in each finger pin are not in the proper position on the side cut, the notches will not rotate to the correct position. The notches will not align with the side bar or let the key rotate the plug. The side bar is non-handed.