What is the primary purpose of a chuck key in metal cutting?

The primary purpose of a chuck key in metal cutting is to loosen or tighten a chuck. A chuck is a clamping device that holds the cutting tool or workpiece securely in place within a machine, such as a lathe or drill press. The chuck key is specifically designed to engage the teeth of the chuck, allowing the operator to apply the necessary torque to either open the chuck to insert or remove a tool or workpiece or to secure it firmly in place for machining operations.

In this context, while holding the workpiece in place is a function of the chuck itself, the chuck key directly performs the necessary action of adjusting the clamping mechanism. The other options, such as transporting materials or reducing tool wear, do not pertain to the specific function of the chuck key and relate more to different aspects of metalworking practices.