Keyed-Alike (KA) Suites vs. Keyed-Different (KD): Lock Pinning Charts & Key Interchange Safety

Executive Engineering Overview

When specifying architectural lock cylinders for residential complexes, commercial retail chains, or infrastructure enclosures, hardware consultants must establish the optimal balance between operational convenience and perimeter segregation. The two fundamental pinning structures are Keyed Different (KD)—where each lock cylinder requires a unique key bitting profile—and Keyed Alike (KA)—where multiple lock cylinders share identical pin chamber stacks to allow a single physical key to operate all locks across a designated suite.

Keyed Different (KD) Engineering & Bitting Permutations

In a standard 6-pin commercial cylinder with 10 bitting depth increments (depths 0 through 9), theoretical mathematical permutations equal 1,000,000 differs. However, real-world mechanical and security constraints govern valid key manufacture:

1. Maximum Adjacent Cut Specification (MACS): To prevent key blade steep angles that cause key insertion sticking or premature key breakage, the maximum allowable depth difference between any two adjacent pin cuts is strictly limited (typically MACS <= 5 or 7).
2. Anti-Interchange Differ Rules: Adjacent depths must maintain a minimum physical step (0.50 mm) to prevent keys from operating adjacent differ codes.
3. Usable KD Codes: After filtering MACS violations and ascending/descending blank profiles, a 6-pin system yields approximately 160,000 to 220,000 certified unique KD codes.

Keyed Alike (KA) Suites & Pinning Chart Formats

In a Keyed Alike suite, all cylinder bodies in the batch are pinned identically. A pinning chart specifies the exact pin codes across all 6 chambers:

• Chamber 1: Bottom Pin #4 (4.50mm) | Top Pin #3 (3.80mm)
• Chamber 2: Bottom Pin #7 (6.00mm) | Top Pin #1 (2.30mm)
• Chamber 3: Bottom Pin #2 (3.50mm) | Top Pin #4 (4.80mm)
• Chamber 4: Bottom Pin #9 (7.00mm) | Top Pin #0 (1.80mm)
• Chamber 5: Bottom Pin #5 (5.00mm) | Top Pin #2 (3.30mm)
• Chamber 6: Bottom Pin #1 (3.00mm) | Top Pin #5 (5.30mm)

Maintaining Physical Security in KA Groups

A common misconception is that Keyed Alike reduces physical pick resistance. Because KA cylinders do not utilize master split wafers (unlike Master Key systems), each pin chamber contains only a single shear line. Therefore, an individual KA cylinder retains 100% of its anti-picking, anti-bumping, and attack resistance ratings equal to an isolated KD cylinder.