How does the micrometer achieve a reading accuracy of 0.01mm?
The correct answer and explanation is :
A micrometer achieves a reading accuracy of 0.01mm through a precisely machined screw and spindle mechanism that allows for fine measurement adjustments. The fundamental principle behind its accuracy lies in the screw thread pitch and thimble scale division.
Explanation (300 Words):
A micrometer consists of a frame, anvil, spindle, sleeve (barrel), thimble, and ratchet stop. It operates using the principle of a screw, where the spindle moves forward or backward when the thimble is rotated.
The accuracy of 0.01mm is achieved through the following design features:
- Precision Screw Mechanism:
- The screw inside a micrometer typically has a pitch of 0.5mm, meaning that one full rotation of the thimble moves the spindle by 0.5mm.
- This fine-pitched screw enables small, controlled movements of the spindle, crucial for precision measurements.
- Thimble and Sleeve Scale:
- The sleeve (barrel) has a main scale marked in millimeters and half-millimeters.
- The thimble is divided into 50 equal divisions around its circumference.
- Since one full rotation moves the spindle 0.5mm, each division on the thimble corresponds to 0.01mm (0.5mm ÷ 50 = 0.01mm).
- Ratchet Stop for Consistency:
- To ensure consistent pressure and avoid measurement errors due to excessive force, a ratchet stop limits the applied force.
- Vernier Scale for 0.001mm Accuracy (in Some Models):
- Some advanced micrometers include a vernier scale, allowing readings up to 0.001mm by further subdividing the thimble scale.
Thus, by combining a precision screw mechanism, finely graduated scales, and a controlled measuring force, a micrometer ensures a highly accurate reading of 0.01mm, making it a fundamental tool in engineering and manufacturing.