5.3.3 Permissible Screw Tightening Torques
Permissible Screw Tightening Torques
The table below lists the maximum tightening torques for DIN 912 / ISO 4762 fixing screws. These values are based on a friction coefficient of u = 0.125 in the as-delivered condition.
Caution
Screws not tightened to the correct torque may cause component damage
- The screw supplier's recommendations must be followed, as they are always binding.
- Low-head screws DIN 6912 should be tightened according to strength grade 8.8.
DIN 912 / ISO 4762 Fixing Screw Tightening Torque Table (u = 0.125)
| Screw | Maximum Tightening Torque (Nm) | |||||||
|---|---|---|---|---|---|---|---|---|
| M6 | M8 | M10 | M12 | M14 | M16 | M18 | M20 | |
| Size BZ | 25 | 35 | ||||||
| Strength Grade | ||||||||
| 8.8 | 10 | 24 | ||||||
| 12.9 | 16 | 40 | ||||||
Torque Application Recommendations
When applying grease containing MoS2 to the guide rail fixing screws and tightening with a torque wrench, a more uniform preload can be achieved. This will significantly improve running accuracy.
Caution
Screws not tightened to the correct torque may cause component damage
- When using grease, especially grease containing MoS2, the friction coefficient u may be reduced by half. Torque values must be reduced accordingly.
Screw Selection Recommendations
- If tension loss is expected, the fixing screws can be treated with thread locking compound
- SCHNEEBERGER recommends using fixing screws with strength grade 12.9
- Use a torque wrench to ensure correct tightening torque
- Regularly check screw tightening status, especially in high-vibration environments
Important Notes
- Friction Coefficient: Table values are based on standard as-delivered condition u = 0.125
- Lubrication Effect: Using lubricants will change the friction coefficient; torque values must be adjusted
- Screw Specification: Per DIN 912 / ISO 4762 standard
- Supplier Recommendations: Screw supplier specifications take highest priority