Vernier Micrometers and Measurement Techniques

Importance of Micrometers

• Used by mechanics to measure wear on parts.
• Two types:
  • Standard Micrometer: Measures to one thousandth of an inch.
  • Vernier Micrometer: Measures to ten thousandths of an inch.
• Choice depends on desired accuracy.

Vernier Micrometer Focus

• Measures within one ten thousandth of an inch.

Preparing the Micrometer

• Ensure measuring surfaces are clean.
• Calibration check:
  • Use a piece of paper or cloth to clean.
  • Close measuring ends with ratchet and check zero alignment on sleeve and thimble.
  • Adjust with a spanner wrench if needed.

Micrometer Scale

• Sleeve has 40 lines; each = 25 thousandths of an inch.
• Every 4th line is longer, representing 100 thousandths.
• Thimble's beveled edge has 25 parts; each = 1 thousandth.
• Full thimble revolution advances spindle 25 thousandths.

Reading a Vernier Micrometer

1. Reading the Sleeve

   • Add numbers to the left of the thimble.
   • Example: Number 1 to the left = 100 thousandths.

2. Counting Lines

   • Count lines between large number and thimble.
   • Example: Three short lines = 75 thousandths.

3. Reading the Thimble

   • Check number lined with sleeve line.
   • Example: Line 9 = 9 thousandths.

4. Reading the Vernier Scale

   • Find line on Vernier that aligns with thimble.
   • Example: Ignore thimble number, align Vernier.

5. Total Measurement Calculation

   • Sum all readings.

   • Examples:

     • Measurement: 1,844 ten thousandths (from example)
     • Situation: Number 3 left of beveled edge = 300 thousandths.
     • Two quarter lines = 50 thousandths.
     • Thimble number 6 = 6 thousandths.
     • Vernier scale alignment = 6 ten thousandths.
     • Total: 3,566 ten thousandths.

   • Another Situation:

     • Number 4 left of thimble = 400 thousandths.
     • Three quarter lines = 75 thousandths.
     • Thimble number 24 = 24 thousandths.
     • Vernier scale alignment = 4 ten thousandths.
     • Total: 4,994 ten thousandths.

Key Takeaways

• Proper calibration and reading technique ensure accurate measurements.
• Understanding and practicing these steps is essential for precision.