Maximum Adjacent Cut Specification (MACS): Key Blade Angle Physics & Pin Wear
Engineering Overview: Technical explanation of Maximum Adjacent Cut Specification (MACS) in key bitting calculations, preventing steep key cut angles and premature pin jamming.
Technical & Engineering Specifications
| Standard | BHMA / Master Locksmith Key Bitting Standard |
|---|---|
| Design Rule | Maximum Adjacent Cut Specification (MACS) |
| Typical Limit | MACS <= 5 depth steps |
| Failure Prevention | Eliminates key binding, blade fracture & pin gouging |
| Bitting Step Increment | 0.50 mm / 0.020 in |
The MACS Engineering Rule
The Maximum Adjacent Cut Specification (MACS) dictates the maximum allowable difference between adjacent pin bitting depths on a key blade (typically MACS $\le 5$ or 7 depth steps).
Why MACS is Non-Negotiable
- Key Angle Physics: Exceeding MACS creates steep cut root angles ($>60^\circ$). When inserted rapidly, the steep slope impacts bottom pins violently, causing key binding or blade snapping.
- Pin Wear Prevention: Keeping cuts within MACS ensures gentle ramp angles, preventing pin tip chamfer rounding over 100,000 cycles.
Frequently Asked Engineering & Selection Questions
Q1: What happens if a key design violates the MACS rule?
The key blade will have excessively steep cut slopes that catch on bottom pins, causing sticky key insertion, pin wear, or broken keys.