Technical

Torque Guidelines for High-Tensile Bolts (Grade 8.8 & 10.9)

S
SRG TECHNICAL TEAM
Metallurgy Specialist
DATE: 2024-05-03TIME: 8 min READ
# Understanding Torque-Tension Relationships For a high-tensile bolt to function correctly, it must be tightened to a specific 'preload'. This preload creates the clamping force that holds the joint together.

The K-Factor (Friction)

Torque is not tension. Approximately 90% of the applied torque is used to overcome friction under the head and in the threads. Only 10% actually creates tension. Lubrication significantly changes these values.

Torque Specifications

The table below provides standard dry torque values for metric fasteners. Always consult your project engineer for specific assembly requirements.
Metric Dry Torque Values (Nm) - Property Class 8.8
SizePitchTorque (Nm)Max Tension (kN)
M61.0011.39.0
M81.2527.316.5
M101.5054.026.0
M121.7593.038.0
M162.00230.071.0

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