How does clamp load relate to torque in fastener seating?

How does clamp load relate to torque in fastener seating?

• A. Torque is the input; clamp load is the resulting clamping force, influenced by friction; proper torque aims for the specified clamp load
• B. Torque and clamp load are the same
• C. Clamp load determines torque but not friction
• D. Torque is independent of clamp load

Answer: (A)

The relationship between torque, clamp load, and friction when seating a fastener is what this question tests. When you tighten, torque is the input you apply. The clamping force that actually holds the parts together—rapidly called clamp load—is the result you get from that torque passing through the threads and under the bolt head. But friction at the threads and under the bearing surface consumes part of that input energy and resists turning, so the same torque can produce different clamp loads depending on lubrication, surface finish, thread condition, and other factors. Because of that, you aim to apply torque that yields the specified clamp load, rather than assuming torque directly equals clamp load. In short, torque is the input, clamp load is the resulting clamping force, and friction is the bridge between them that makes the relationship variable.

The relationship between torque, clamp load, and friction when seating a fastener is what this question tests. When you tighten, torque is the input you apply. The clamping force that actually holds the parts together—rapidly called clamp load—is the result you get from that torque passing through the threads and under the bolt head. But friction at the threads and under the bearing surface consumes part of that input energy and resists turning, so the same torque can produce different clamp loads depending on lubrication, surface finish, thread condition, and other factors. Because of that, you aim to apply torque that yields the specified clamp load, rather than assuming torque directly equals clamp load. In short, torque is the input, clamp load is the resulting clamping force, and friction is the bridge between them that makes the relationship variable.