Final answer:
The chuck key must be removed from the chuck after the workpiece is securely clamped to ensure safe operation of a lathe machine.
Step-by-step explanation:
The lathed chuck key should be removed from the chuck after clamping the workpiece securely. In a lathe machine, the chuck is used to hold the workpiece in place while it is being machined.
The chuck key is an essential tool for tightening or loosening the chuck, but leaving it in the chuck while the machine is in operation can be incredibly dangerous, as it could be thrown out at a high speed. It is crucial for safety to always remember to remove the chuck key immediately after securing the workpiece.