Under what circumstance is it acceptable to leave the cutting tool or workpiece rotating when taking a measurement?

• A. Your hand is several inches away from making contact with the tool or workpiece
• B. The tool or workpiece is rotating less than 500 rpm
• C. You feel confident you have one too many fingers on your measuring hand
• D. None of the above

Answer: (A)

The essential idea is to keep yourself out of the path of rotating parts. When a tool or workpiece is turning, contact can occur suddenly from chip ejection, kickback, or an accidental slip. If your measuring hand is several inches away from making any contact, you reduce the immediate risk of injury, making this the only circumstance among the options that allows measuring without stopping the rotation. In practice, the safest approach is to stop the machine before taking measurements, but distance without contact is the only scenario here that aligns with doing measurement around rotating parts without immediate danger. The other options imply direct risk (even at low speeds) or unsafe conditions, so they aren’t appropriate.