How do you determine torque required to tighten a bolt to a given tension?

How do you determine torque required to tighten a bolt to a given tension?

• A. Torque is proportional to bolt color
• B. Bolt length
• C. Not related
• D. Torque-tension formula

Answer: (D)

Tightening a bolt to a specific tension relies on the torque-tension relationship. The torque you apply must overcome friction in the threads and under the bolt head while providing the desired clamping force, so you can’t just guess torque without accounting these factors. In practice, this is captured by a torque-tension formula, which links the clamping force (bolt tension) to the applied torque through a factor that reflects thread pitch, diameter, and friction (often written as T = K · Ft · d or a similarly arranged form). This means the same torque will produce different tensions depending on lubrication, surface finish, and whether the threads are dry or lubricated; reducing friction lowers the torque needed for the same tension, while increasing friction raises the required torque. The other statements don’t describe this essential linkage: color has no bearing on the torque-tension relationship, bolt length mainly affects strength and load path, and saying it’s not related ignores the very dependence on friction and geometry.

Tightening a bolt to a specific tension relies on the torque-tension relationship. The torque you apply must overcome friction in the threads and under the bolt head while providing the desired clamping force, so you can’t just guess torque without accounting these factors. In practice, this is captured by a torque-tension formula, which links the clamping force (bolt tension) to the applied torque through a factor that reflects thread pitch, diameter, and friction (often written as T = K · Ft · d or a similarly arranged form). This means the same torque will produce different tensions depending on lubrication, surface finish, and whether the threads are dry or lubricated; reducing friction lowers the torque needed for the same tension, while increasing friction raises the required torque. The other statements don’t describe this essential linkage: color has no bearing on the torque-tension relationship, bolt length mainly affects strength and load path, and saying it’s not related ignores the very dependence on friction and geometry.