What is the most important rule when using manual lathes?

• A. Wear gloves
• B. Never leave chuck key in chuck
• C. Keep your lunch nearby
• D. Use coolant at all times

Answer: (B)

The main idea is safety discipline around rotating machinery, and the most important rule is to remove the chuck key before turning on the lathe. If the spindle starts with the key still in the chuck, the key becomes a dangerous projectile that can strike hands, eyes, or other body parts and can cause serious injury or damage to the machine. It’s a quick, simple check that prevents one of the most common and severe lab injuries, so it’s drilled into every lathe user from the start.

Gloves around a lathe can snag on moving parts and pull your hand into the chuck, so they’re generally avoided during operation. Lunch nearby is unrelated to safe machining practice, and coolant use depends on the operation and material, not a universal requirement.