Overview
This lecture explains how to use and read an outside micrometer to make precise external measurements, focusing on how to interpret sleeve and thimble readings.
Introduction to Micrometers
- A micrometer measures very small, precise lengths that can't be estimated by sight.
- An outside micrometer is used for measuring the external surfaces of objects.
How to Use a Micrometer
- Place the object between the anvil and ratchet of the micrometer.
- Tighten the device to secure the object in place for measurement.
Reading the Micrometer
- Read the sleeve first; whole numbers equal 0.10 inches.
- The short quarter marks between whole numbers on the sleeve represent 0.025 inches.
- Add whole numbers and quarter marks on the sleeve for the sleeve reading.
- Next, read the thimble; large marks represent 0.001 inches.
- Shorter marks on the thimble equal 0.0005 inches.
- If the reading line is between two numbers, always use the smaller number.
- Add together the sleeve and thimble values for the total measurement.
- Example: 0.3 (three whole numbers) + 0.05 (two quarter marks) + 0.0005 (first short mark) = 0.355 inches.
Key Terms & Definitions
- Micrometer — A tool for precisely measuring small distances.
- Anvil — The stationary measuring surface on a micrometer.
- Ratchet — The mechanism that tightens and holds the object in place.
- Sleeve — The part of the micrometer with main scale marks (whole and quarter).
- Thimble — The rotating part with fine scale marks for additional precision.
Action Items / Next Steps
- Practice reading measurements on a micrometer.
- Review differences between sleeve and thimble readings.