What is the proper name for the tool used to create threads on a steel pipe?

The tool specifically designed to create threads on a steel pipe is known as a die. A die is a precision tool used in metalworking that is fabricated to cut external threads onto a pipe's surface when it is turned. By using a die, a technician can ensure that the threads are uniform and properly shaped to match the specifications needed for connections with fittings or other pipes.

In the context of this question, the other tools serve different purposes. For instance, a pipe wrench is typically used for gripping and turning pipes, especially in applications where manual torque is required. A pipe cutter is designed to cut through pipe materials cleanly and efficiently, while a threading machine is an automated tool that can also create threads, but it is not called a "die." Understanding the specific functionalities of each tool clarifies why the die is the correct answer for threading purposes.