How does a torque wrench ensure proper fastener preload?

How does a torque wrench ensure proper fastener preload?

• A. It measures temperature
• B. It applies a precise torque to achieve the recommended clamping force and prevent over- or under-tightening
• C. It lubricates the bolt
• D. It cuts the bolt to length

Answer: (B)

The main idea is that preload—the clamping force in a joint—is controlled by applying a precise torque. A torque wrench delivers an exact torque value, so tightening to the specified amount brings the bolt to the intended preload. The actual clamp force depends on friction in the threads and under the bolt head, as well as any lubrication and the bolt’s geometry, but the torque spec is chosen to produce the recommended preload safely. If you go higher than the spec, the joint can be overstressed or the threads can be damaged; if you go lower, the preload may be insufficient and the joint can loosen under vibration. This tool isn’t about measuring temperature, lubricating the bolt, or cutting the bolt length.

The main idea is that preload—the clamping force in a joint—is controlled by applying a precise torque. A torque wrench delivers an exact torque value, so tightening to the specified amount brings the bolt to the intended preload. The actual clamp force depends on friction in the threads and under the bolt head, as well as any lubrication and the bolt’s geometry, but the torque spec is chosen to produce the recommended preload safely. If you go higher than the spec, the joint can be overstressed or the threads can be damaged; if you go lower, the preload may be insufficient and the joint can loosen under vibration. This tool isn’t about measuring temperature, lubricating the bolt, or cutting the bolt length.