What is the primary function of a torque wrench?

A torque wrench is a specialized tool designed to apply a specific amount of torque to a fastener, which is typically a bolt or nut. This ensures that the fastener is tightened to the manufacturer's specifications, which is crucial for maintaining the integrity and safety of mechanical assemblies. Tightening bolts to an exact torque is important because improper torque can lead to mechanical failures, such as leaks in fluid systems or the loosening of parts during operation.

In this context, the other options do not fulfill the primary function of a torque wrench. Measuring engine speed pertains to diagnostic and performance tools, changing tire pressure involves inflating or deflating tires using gauges or air compressors, and cutting through metals relates to metalworking tools like saws or shears. Each of these tools serves a different purpose and does not relate to the specific functionality of a torque wrench.