In a micrometer, which mechanism is used to ensure consistent contact pressure during measurement?

• A. Ratcheting screw
• B. Vernier scale
• C. Thimble scale
• D. Anvil

Answer: (A)

Consistent contact pressure in a micrometer is achieved with the ratchet mechanism on the handle. As you rotate to bring the spindle toward the anvil, the ratchet allows the spindle to press with a steady, predefined force and will slip or click once that torque is reached. This prevents you from squeezing harder and deforming the workpiece or altering the reading, giving repeatable measurements regardless of your grip. The other features have different roles: the vernier scale and the thimble scale are for reading the spindle position with precision, while the anvil is the fixed contact surface. They don’t regulate how hard the spindle presses, which is why the ratchet mechanism is the correct choice.