What is the correct use of a torque wrench in assembly?

• A. To apply a specific, prescribed torque to fasteners to achieve proper clamping force.
• B. To loosen bolts by turning them until they strip.
• C. To measure torque approximately.
• D. To lubricate fasteners.

Answer: (A)

The key idea is using a torque wrench to control the clamping force in a joint by applying a precise, prescribed torque to each fastener. When you tighten bolts or screws to a specific torque, you achieve a known preload in the fastener, which clamps the parts together with the right amount of force. This precise control helps ensure the joint remains secure under service loads without risking damage from over-tightening (which can strip threads or stretch the bolt) or from under-tightening (which can allow movement or loosening).

A torque wrench is calibrated to a value specified by the assembly instructions, and those values are chosen based on fastener size, thread pitch, lubrication status, and the number of fasteners in the pattern. Using the tool to reach that exact torque makes tightening repeatable and reliable across all fasteners in the assembly.

The other ideas don’t fit the intended use: loosening bolts by turning until they strip is dangerous and not how you achieve proper preload; estimating torque without a tool sacrifices precision; lubrication affects the torque needed but isn’t the function of the wrench itself—torque values assume proper lubrication and are used to set the correct application of torque.