Final answer:
The lathe chuck should be removed from the spindle when it is no longer needed or when you need to replace it with a different chuck or tool.
Step-by-step explanation:
The lathe chuck should be removed from the spindle when it is no longer needed or when you need to replace it with a different chuck or tool. Removing the chuck allows you to safely and easily access the spindle for maintenance or other purposes.
For example, if you are using a lathe chuck to hold a workpiece for machining, you would remove the chuck once you have completed the required operations on the workpiece.
Another instance where you might need to remove the chuck is when you need to clean or lubricate the spindle to ensure its proper functioning.