Mr Hassan’s Micrometer Lab

Routine

1. Sleeve first: last visible whole mm, then check if the 0.5 mark is visible.
2. Thimble second: the division that lines up with the datum line.
3. Add: sleeve + thimble = observed reading.
4. Correct: corrected = observed − zero error.

Practical precautions

• Use the ratchet/thimble to apply constant pressure (avoid deforming the object).
• Measure at right angles to the wire.
• Take readings at several points along the wire and rotate it.
• Check and correct for zero error before/after.
• Keep the faces clean; avoid kinked/flattened regions.
• Read square-on to reduce parallax.