Fastening Torque Limits for M5 Cylinder Retaining Screws: 3.5 to 4.5 N.m
Engineering Overview: Installation guide specifying M5 cylinder retaining screw torque limits (3.5 - 4.5 N.m) to prevent brass bridge distortion and plug binding.
Technical & Engineering Specifications
| Fastener | Metric M5 x 65 mm / M5 x 75 mm Countersunk Screw |
|---|---|
| Failure Mode | Over-tightening bends central bridge, seizing plug rotation |
| Thread Pitch | M5 x 0.8 mm Standard Metric |
| Recommended Torque | 3.5 - 4.5 N.m (Hand Tighten Only) |
The Over-Tightening Hazard
The lateral M5 metric fixing screw holds the cylinder inside the mortise lockcase.
Fastening Torque Specifications
- Recommended Torque: 3.5 N·m to 4.5 N·m using manual hand screwdrivers.
- Failure Mode of Over-Tightening: Exceeding 6.0 N·m with power drills bends the slender 10 mm brass waist of the cylinder, pinching the internal rotating plugs and causing severe key stiffness or lock seizure.
Frequently Asked Engineering & Selection Questions
Q1: Why shouldnt an impact driver be used to tighten cylinder M5 screws?
Impact drivers easily exceed 10 N.m torque, which bends the central brass bridge and causes the lock plug to bind and stick.