What operations can a milling machine not perform?

A milling machine is a versatile tool primarily used for cutting and shaping metal and other materials. It excels at removing material from a workpiece, which is its fundamental operation. Additionally, milling machines can perform various tasks including drilling holes and cutting complex shapes due to their ability to use different types of cutting tools and adapt to various setups.

Threading is a specific operation that typically requires a different type of machine, commonly a lathe. While some milling machines may have capabilities to create threads using special attachments or tooling, this is not their primary function, and they are not generally designed as threading tools. Therefore, the option about threading bolts accurately identifies an operation that is not standard for milling machines, making it the correct choice in this context.