When it comes to cutting keys, there’s more at stake than just matching the right bitting numbers. One critical factor locksmiths consider is the distance between adjacent key cuts — and that’s where MACS (Maximum Adjacent Cut Specification) comes in.
The Problem with Drastic Cut Differences
Each cut on a key corresponds to a pin inside the lock. But if one cut is very deep and the one next to it is very shallow, the shallow cut can become a weak point. This dramatic step down in height between cuts can causes the shallower cut to be removed by the key cutting machine.
Here’s why it’s risky:
The shallow cut can be unintentionally “erased”: When key cuts are too far apart in depth, machines or manual cutters can accidentally remove the shallow cut entirely, especially if it sits right next to a deep groove.
Compromised key function: Without that shallow cut, the key won't lift the pin stack to the correct shear line, causing the lock to jam or fail to turn.
What Is MACS?
MACS stands for Maximum Adjacent Cut Specification — a limit that defines how different the depths of two neighboring cuts on a key can be. It's built into professional keying systems to ensure durability, functionality, and accuracy.
For example, if a lock has a MACS value of 4, and one cut is a 1-depth, the cut next to it cannot be deeper than a 5. If you tried to make the next cut a 6 or 7, you'd exceed MACS — and risk the problems described above.
Why It Matters for You
When we create or duplicate keys at Everything Locks, we carefully follow MACS guidelines to make sure:
Shallow cuts aren't accidentally wiped out during cutting
Keys won't fail prematurely from wear or stress
Locks continue to operate smoothly and reliably
Ignoring MACS doesn’t just lead to a bad key — it can damage the lock itself over time, or leave you locked out when the key wears out unexpectedly.