How is torque defined in fastening applications?

How is torque defined in fastening applications?

• A. The axial force only
• B. The turning force applied to a fastener to achieve the desired clamping load.
• C. The friction coefficient
• D. The speed of the fastener

Answer: (B)

Torque is the turning force you apply to a fastener to generate the clamping preload that pulls the joint together. When you twist a bolt, the rotation is transformed into a linear pulling force along the fastener’s axis, which clamps the parts. How much clamp you achieve depends on the torque you apply and how much resistance (friction) is present in the threads and under the head. In practice, engineers use the relation T ≈ K · F · d, where T is the torque, F is the preload (clamping load), d is the nominal diameter, and K is a factor that captures friction and thread geometry. So the essence is that torque is the turning effort that creates the desired clamping load; it isn’t just an axial force by itself, nor is it set by friction coefficient alone or by speed of the fastener.

Torque is the turning force you apply to a fastener to generate the clamping preload that pulls the joint together. When you twist a bolt, the rotation is transformed into a linear pulling force along the fastener’s axis, which clamps the parts. How much clamp you achieve depends on the torque you apply and how much resistance (friction) is present in the threads and under the head. In practice, engineers use the relation T ≈ K · F · d, where T is the torque, F is the preload (clamping load), d is the nominal diameter, and K is a factor that captures friction and thread geometry. So the essence is that torque is the turning effort that creates the desired clamping load; it isn’t just an axial force by itself, nor is it set by friction coefficient alone or by speed of the fastener.