Yes, a milling cutter can be used to mill an external thread. This process is called thread milling and it involves using a specially designed cutter to create the thread profile in one or multiple passes. Thread milling can be used to create threads of various sizes, including larger ones that may not be feasible to cut using a tap or die. It can also be used to machine threads on non-axisymmetric surfaces and in hard materials such as hardened steels.