Final answer:
The correct phrase to ensure the milling machines and lathe are ready to be turned on is 'safe range'. This ensures both operator safety and the proper functioning of the machinery.
Step-by-step explanation:
The phrase that correctly completes the sentence 'Always check the milling machines and lathe are in ________ range before turning them on?' is option 2) safe. It is crucial that the equipment used in machining is within a safe operating range to protect the user and ensure the longevity of the machinery. This includes verifying that all parts are secured, the machine is set to the correct speed for the material being worked on, and that there are no visible issues that could pose danger during operation.